You're not presenting data though. You're taking Mearls's word for it.
Yes. That's right. I am assuming there is not some vast conspiracy at WOTC to torpedo their own department, and all their own jobs, by forcing D&D in a direction that runs contrary to the data from their customers.
Extraordinary claims require extraordinary proof. Unless you have proof of this conspiracy based on a huge lie, you should cut it out.
Yes, it is a reasonable, rationale thing to do to assume that Mike Mearls is telling the truth when he reports that the data they got back is what he says it is.
Games are realizing that you can ignore sacred cows, and games like Fate Core are gaining ground.
Here is some useful data.
D&D 5e: 60.71%
FATE: 0.78%
FATE is literally a rounding error right now for D&D (and the gap is actually widening over time, as FATE goes down and D&D goes up).
That's no dig on FATE. If that's your game, go have fun with it. But don't pretend FATE is proof of something for D&D. If anything, the data says drastically different.
I realize you can't argue on the merits
Oh no, that is not what I am saying at all. I am saying the merits are not what you think they are. Merits means, "the quality of being particularly good or worthy, especially so as to deserve praise or reward." It's an overall macro claim, not a micro claim. You think the merits are things like DPR and replication of skills via spells and that sort of number crunching. That's not the merits, those are microscopic details of sub-categories of small aspects of the game. No, the merits are, "what issues seem to be making the game more or less fun, in a meaningful way, for a vast majority of people likely to play the game". THOSE are the merits of this game that I am insisting you at least take into account.
so you insist on people producing data that's impossible to get a hold of
No I am not. I am asking that, unless you make a claim about what your personal preference might be (in which case, you need no proof), when you're making broad based claims about "things that make the game unfun" or "things which make people not want to play the game", then you have data to support those claims which is at least equal to the data I am mentioning.
What I'm saying is that it would have a lot more broad appeal--and be more fun for me personally--if they had made more of an effort to make sure that all classes could contribute in meaningful ways outside of the combat minigame.
You can say it would be more fun for you personally. But you cannot back up the claim that it would have a lot more broad appeal if it conformed more to your personal preference - not when the only data we DO have runs contrary to that (that a representative sampling of the playtesters, who came from a diverse variety of backgrounds and preferences, all liked it in actual play). And when I ask you to back up that claim, and you fail to produce even a mere scintilla of evidence to back it up, I am calling you out on it.