For some reason, your question about defer dates in Reminders sounded familiar.
No offense, just pointing out your previous topics, one of them actually being quite a good starting point to give you some ideas. 
As you already have noted, there is no dedicated defer date field, only one date field and one time field when creating a reminder. Those fields are basically “due” dates (or times).
If you absolutely need several date/time fields, you will not be able to use Apple’s Reminders app for your task management. There is a reason why OmniFocus is out there and successful: it has a different approach with more features. And it does add some complexity to GTD that is welcome or even necessary for some and not so much for others.
I am one of those who switched from OmniFocus to Reminders about 1 or 2 years ago after a long period of switching between Things, OmniFocus, and Reminders. All of those apps have something that they are doing best. Reminders is the one that fits my needs most. So, are you completely out of luck with Reminders and defer dates? No. It depends. Apple has created the option to create smart lists.
You can basically go nuts on smart lists, using those due dates, maybe even bring some tags (#deferred, #firstquarter, #secondquarter … #deferred_until_2027 …) or flags into the mix and so on. Depending on how you organize yourself, you can create a surrounding in Reminders that is extremely powerful and complex. There may be a recent field guide out there to give you some ideas (Apple Productivity Suite Field Guide (Essentials)) | MacSparky Field or Apple Productivity Suite Field Guide (Expert) | MacSparky Field Guides). 
To make it short: if you absolutely need an individual date field for every task to judge if something can or should be deferred, Reminders may not be your tool. If you are able to find a way to use smart lists to define more abstract criteria, if something can or has to be deferred right now, then Reminders is all you need.
One of the reasons I switched from OmniFocus to Reminders is that defer dates are not that interesting to me, so I may be the wrong person to give you ideas, but @Bmosbacker for instance has published quite some insightful posts on this matter that may give you some ideas:
A direct answer to your question in 2021. Your answer there:
My answer to that would be: smart lists will hide stuff until it’s time to start doing something as long as you are able to define in an abstract way some criteria, when exactly it is time to start doing something (using due dates and/or tags and/or flags).