You made great points! 
The last thing I want to do is to waste time. I see no value in investing time to, for example, create compatibility for TinyMCE v5 with WP 4.9. Well yeah, the idea of compatibility is beautiful but when you start to even look at it… there isn’t any joy at all that can be found in executing such a task!
And that’s what happening, many things are just abandoned because trying to stick to that idea is almost impossible. On the other hand, working on things without the burden of compatibility would be easier and definitely more fun, which will also by the laws of nature attract more developers.
Sure, other things can be done too, but it’s all part of the same rocket. So I have to like where the rocket is heading to first.
So I will stay tuned and when/if the CP community part that wants to “move away from WP” as you call it gets bigger than the other one, then I will definitley roll my sleeves up, probably even tear them off the shirt. Of course I will have ideas that don’t resonate with the community goals, and I will be okay with that. But at least a small percent of flexibility has to exist, or this will just be a long and boring todo list that never gets done.