Everyone? I have not suggested anyone should leave or not participate, let alone everyone.
I have problems with non-magical "magic" like healing, I have issues with daily/encounter/etc powers, especially when they are non-magic Magic (including the ones in 3.5), and I don't like some of the 4e terms used, especially those overly game-y. I dislike the overly tactical nature, at the expense of the feel (for me, ymmv)
If too many of those things are in the base system of 5e, it will not be something that appeals to me or the dozen or so people I game with. If that's the case, we'll continue to take our dollars elsewhere. I am about 99% sure I am not alone in disliking many of those changes.
On the other hand, I don't want THAC0 coming back, Non-Weapon Proficiency, Demihuman level limits, CODZilla, PunPun, 18/00 strengths, 20d6 fireballs, or any of that stuff either. The difference? They aren't talking about putting the stuff I don't care for from older editions back into the new system. And if they start talking any of those, I'll be railing against those as well.
I know WotC people frequent these forums, and it would do everyone a disservice if the only feedback they got was people praising everything. I don't feel that making it known that some of these things are deal breakers is out of line. Whether the game succeeds or fails, they should at least hear from people what they do and don't like, so they can't claim ignorance.