You don’t need a classy DSLR to outclass an iPhone. As mentioned above, an 11 year old DSLR is producing better pictures than a 1 year old phone.
I love owning a camera that delights me and teaches me how photography works. And because I have had several of those over the years, I’ve had less iPhones. I know some people are delighted by iPhone cameras and all power to them, but what I want to shoot is completely unsuited to iPhones.
So true. Get yourself a cheap (or used) DSLR with a nifty fifty, get out and start playing with aperture and shutter speed and you eventually will forget (almost) everything about “machine learning”, computational photography and so on…
Disclaimer: I do not want to be harsh on the iPhone cameras. They are getting better and better. And Apple’s software is doing a mind-blowing job getting most out of the limited optics and the (still) small sensor inside the iPhones. If there was an Apple DSLR with adapters for Canon and Nikon glasses, other manufacturers probably would have a very hard time to sell anything.
There is no right or wrong in this iPhone vs DSLR discussion. And for more and more users who never want or never will do manual photography a good camera inside of a smartphone will do the job, but if you “embrace” photography, you will achieve results and a beauty shining from your pictures with cheap DSLRs and with cheap lenses that is unparalleled.
There ARE situations in which iPhone cameras get results that are very hard to distinguish from DSLR shots. But even with my iPhone 12 Pro Max, there are sometimes situations which make me cringe. 
My dog has hair. Under ideal circumstances, the hair shows up as hair (yes, I know about the “sweater” mode a.k.a. Deep Fusion). But then, it does not. And it looks like one big pixel noise mess.
And yes, Austin Mann shows it time and again what amazing results you can achieve with an iPhone.
Imagine, what he can do with a DSLR… 
Trat’s true. As for GPSes, Calendars, etc.
Well put on all counts.
There are also situations where the iPhone can achieve the same as the DSLR but the DSLR will take a lot more work, or skill. I’ve taken only a handful of “night mode” shots on my 11 Pro but man it was impressive to watch the image build up in front of my eyes until it was exposed just right.
For me it is landscape with haze. A few lines of hills in the background make for some stunning harbour vistas where I live, but the iPhone shots always turn those hazy hills into mush.
And… one point you didn’t cover… if it weren’t for iPhones, a lot of people who today take lots of photos would take no photos. That’s a net positive despite the Instgramification factor.
I forgot a point about this. I have my DSLR to take high quality photos and now I have software which uses machine learning which makes my DSLR photos even better.
I had been using DxO PhotoLab 3 for about a year and loving how crisp and clear my shots were coming out. Recently they launched version 4 which uses machine learning to both demosaic and denoise in one step and the results are frankly stunning. Then if your photo isn’t big enough (say for printing at an enormous size) you can run it through Pixelmator Pro’s machine learning-powered upscaling feature, which I have done some fairly challenging testing on and can attest is amazing.
Right. There is a “democratisation” argument to be made about mobile phone photography. But it’s still a, to use the cliché, “rich person’s sport”.
Nonetheless camera phones have opened up photography to many millions of people.
A cheap/used DSLR will mostly be APS-C, so rather get a 30/35m. Even on FF/FX, I prefer 35.
APS-C or Full Frame: yes, a Full Frame camera is nice, but in comparison to a smartphone, an APS-C DSLR with a lens still will blow the phone out of the water. It all comes down to the optics. I am a Canon guy. I have been using the Canon Rebel Series APS-C models for many years until I bought a 5D Mark II when its price came down (the 5D Mark II still is an awesome camera today although it is way outdated). The step up to full frame was very nice, but the photos were not bad before that either. This year I donated myself a Canon EOS RP (more than enough for me). Full Frame photography has become affordable. But any DSLR will give you a lot, no matter if APS-C or Full Frame. Learning and using the exposure triangle can be a lot of fun, regardless of the sensor size (even on an iPhone with apps like Halide).
@zkarj - I can only return what you wrote about my post: well put! 
I have to be honest: I do not consider myself a good photographer. I have been impressed with several shots on my iPhone - I am not sure, if I could have achieved the same with my skills on my DSLR. Sometimes the processing on the iPhone is just great. Thank you for mentioning DxO PhotoLab - something to check out eventually!
Just wanted to add on the recommendation for a 50mm. I don’t think it’s a good suggestion for APS-C/DX users. It’s a often read suggestion and most people buying a 50mm lens end up not using it, because it’s frustrating on a crop sensor camera. As stated, even on full-frame, I`d rather get a wider one (30/35) as the first prime lens.
I agree to disagree on that one. Let’s just say that I have been very happy with this lens and I can recommend it to everybody wholeheartedly. 
Now you all have me intrigued by the idea of getting an 11 year old DSLR. What should someone buy when shopping for a old DSLR?
Depends on your budget.
I am a Nikon guy:
I wouldn’t get anything older than those, the D200 if a bargain is found, might be the exception. Skip any D600, D610 is OK. The D3xxx are toys, at least a D5xxx.
Depends on what you are willing to spend and what compromises you are willing to take. I have some ancient D70s and a D200 lying around (remote camera when camera loss is probable), low-light performance sucks.
If you choose Canon, the 5D Mark II still is a nice camera. Nikon is great, too. 
If you buy a used camera, you should buy from a trusted seller. If you can, you buy locally in a camera shop (if you can find one). Check the camera for dead pixels, dirt, dust, mechanical issues and its shutter count. More at https://photographylife.com/how-to-buy-used-dslr-cameras Sounds frightening? Buy from a trusted seller.
Do not spend more than a few hundred bucks on a used DSLR because the prices for full frame cameras keep coming down…
People who are disappointed with a 50mm lens on an APS-C camera perhaps do not understand what they are getting — i.e. an equivalent 75 or 80mm lens (APS-C isn’t completely a standard!). Personally I have a 50mm f/1.4 which is a beautiful portrait lens, though I shoot very few portraits.
On what to buy… there are so many options and you could spend weeks researching, but I do recommend researching old reviews. Personally, my Dad was a Pentax user and so my brother was a Cosina (Pentax system equivalent) user and my first SLR was inherited from him and so I still rock a Pentax to this day. And best of all, I get to use Dad’s old lenses that he bought in the 70s, along with more modern stuff I’ve bought new and a handful of “vintage” manual lenses, too (one of which I was given for free). The 11 year old camera I referred to above was a Pentax K10D, which was great except in low light. It’s still in use with a new owner.
For the record, I’ve spent more on D/SLR cameras than iPhones. I’ve bought five of them and… counts on fingers… six iPhones. But I also undertook the “hundred dollar camera project” wherein I purchased a cheap (less than USD)$100 camera from a local electronics retailer in order to prove that it can take photos as good as an iPhone, at least in good light. And it does. But, it also takes better photos because it has a built in 28mm-224mm equivalent zoom lens and 20 megapixels.
If you’re a person who buys the Pro Max because of the better camera, you can get a 12 Pro and spend the $100 saving on a hundred dollar camera to get decent quality and vastly superior zoom. And if you want super low light or wider than 28mm equivalent (the “middle” lens on iPhones is 26mm), well, you’ll still have your iPhone for that. Though I don’t expect many people would go for this option — I certainly wouldn’t except to prove a point. 
I don’t even want to calculate the amount of money that’s in my photography gear drawer(s).
I bought a D200 in 2006. It served me very well. Those 10 megapixel images still hold up superbly. Nothing I can produce on my iPhone 12 Pro comes close to those photos.
Of course the iPhone has all the advantages that have been mentioned in this thread, and it’s the only camera I have now. But even with it’s clever computational photography, the final output is always disappointing when I compare it to any halfway decent DSLR.
One day when I have more time I will buy a full frame camera of some form.
I agree with @Lars and @Christian recommendations, especially this one:
If you want to consider a smaller and lighter camera you could opt for a mirrorless, like the fujifilm x-t2/3. On mirrorless camera is easier to adapt vintage lenses too 
Ok, let’s go into the rabbit hole…or buy a film camera… 
Yep - I have an ME Super which was given me by my uncle who was a pro cameraman. I don’t use the camera often but I love the results of the 50mm prime on my Olympus M4/3 kit.
I’m probably shopping in the $200 camera range and not the $500 range. $500 plus a lens is real money!
The nearest camera stores are an hour away from me. It will be a while until I travel that far for a shopping trip which should give me plenty of time to research and decide on a camera.