As a non-programmer artist I won't pretend to understand what is involved in adding new features, and while I have my own wish list of what I want improved, I know that everyone who uses C4d has their own as you stated. On it it's own I love the idea of the subscription model, I just wish I hadn't purchased studio for the first time earlier this year because I am getting screwed hardcore for not waiting 6 months, and as a small time freelancer that is devastating. I used to use 3ds max where I had to buy several plugins to get everything I needed (liquids, smoke, renderer, etc.) although that has changed quite a bit since I left. Cinema 4d seems to be going down this same road which makes me cringe. There are also some basic areas Cinema 4d lacks compared to other major 3d packages (modeling, UV's, Viewport, etc.) and I hope these areas will be addressed soon. I love cinema 4d for many reasons (Mograph, Animation, Sculpting, Takes, etc.) but having to wait extended periods of time for features that other packages have, and continue to improve upon will eventually make it harder to stay. R21 itself has plenty of small quality of life improvements that I look forward to using on a daily basis. The same was true for R20. At some point though, other 3d packages might become worth the gamble if Cinema 4d can't keep up or even gain ground. Personally, I hope that isn't the case as I have gone from Maya to 3ds max and now Cinema 4d. Ultimately I will use the best tool for the job, and while that is currently Cinema 4d for what I do, that could quickly change.
--Shadd