Yeah, this is a great theory. However, walking out of the office at 1:30 PM, telling your boss it’s all done and you’re off to the gym/golf course/pub/whatever isn’t going to go over well in corporations. Employers will still consider they pay you for time, not output.
When working for yourself, or possibly, working from home, this balance may be easier to strike.
While this is true it is basically a flaw in our working culture and I sincerely hope that this attitude will change in the future.
Nice points; truth is in my view and experience that what really happens overall is that less people are required to do the same amount of work. It is the automation paradox you might say. The issue is complicated though and pure ‘productivity’ doesn’t address it really, not these days anyway. In my own case I made several major streamlines in various capacities over the years. They just cost jobs in the long run though, at the same time, we are producing a lot more than we were. Too much some might say. I don’t see the central issues as lying with IT as such.
I’m one of those people who has collected a large number of apps over the years. A colleague just purchased an iPad Pro and asked for recommendations and I told him I was going to cost him lots of money. As I started looking through my long list of apps I really only found a very few that I would call “essential”. I’m now in the process of weeding others out.
As much as I like simple and effective, there are times when a specific application is a time saver or super useful.
There is a time and place for automation. I have never delved in to Workflow app. I am a huge fan of simple.
There is a point to keeping apps that are useful and using what you have. Balance is a beautiful thing.
I highly recommend the two books by Cal Newport: Deep Work and Digital Minimalism. I have read both and found them to be compelling. And, as many readers on this formal know, Cal is an MIT level computer scientist—he is no Luddite. 
I like trying new apps, it is like a form of entertainment. But when it comes to doing my work (software development), I’m actually pretty conservative in allowing new tools into my workflow. My daily code editor is still vim, which is how many decades old? I know there are probably better tools, but since I mastered vim many years ago, I just don’t think it is worth switching at this point. Besides vi is installed on every unix server ever deployed.
I don’t think the number of tools you use have much to do with deep or shallow work with the exception of interruptive tools like chat. Digital minimalism has more to do with social media and your personal life.
Your job description drives the variety of tasks you do (which correlated to the number of apps you use) and also to the percentage of them that are best done in deep focus. The degree to which you defragment your work week affects task switching costs more than the tool you use for each task.
I am certainly for clearing out ineffective workflows and barely used tools, but if your job or organization isn’t changing any time soon, studying and mastering all those tools you use seems at least as viable a path to increased effectiveness. You might even become more certain about the limits of what you’re using and add something new.