So, a couple things:The bolded part is probably true if the goal is to make a really well-designed game.
That is not the first priority of WotC as far as D&D is concerned; the first priority is to make a very popular game.
And, ya gotta admit, it's working.
"Well designed" and "popular" are not mutually exclusive.
Also, I do think that 5E is "well designed" in a general sense, but I also think that it is a) old, b) has some obvious flaws, and c) does not address some pretty significant very D&D concerns in any meaningful way.
So my problem is that marketing stunts dressed up as public playtests do not address any of those things, and actively hold back design innovations because the people that respond to surveys are the most likely to be strident about preferences.
@Hussar keeps asking for evidence and I would point them to the American political primary system as well as every beta test ever. It is known to be true that more invested individuals with more strongly held positions are more likely to engage in these things. This isn't controversial. It's just how humans do.