Great overview, i am thankful that accessibility was mentioned as well.
Inevitably someone complains about lack of accessibility of a custom UI toolkit, which is frustrating, because something that helps 99% of people is still an improvement and still worth doing.
I do agree about the idea though. We shouldn't shut down experiments just because they don‘t have a plan for it yet. I do see some of that on twitter etc. But once you‘re shipping software that users can‘t switch away from, because of network effects or because it‘s at work, it‘s not ok.
Also, yeah, I (not OP) depend on it.