Hiya!
I guess the closest I can come is this: WotC seems to be trying to focus attention on THEIR characters and not YOURS/OURS.
I don't want to be constantly reminded of how great Mordenkainen is, or how awesome Elminster is, or how super-secretive-but-everyone-knows-him-and-is-afraid-but-not-really that Xanathar floating orb monster is, etc. I don't want to hear "Oh, Mordenkainens Foes book has those guys" because it ever so slightly denigrates the monsters in it to be somehow related to Mordenkainen. If I write a series of adventures centered around some creature to be found therein, no matter how unique and memorable my adventure is...both the players and I will ALWAYS "know" that "Mordenkainen knew all about those guys first". Supplemental books for AD&D were generic. They were tools for us to use to tell our own stories and have our own tales of heroics. Now? Well...
I don't want to be reminded of how cool and wonderful WotC's IP is. I want WotC to produce products that focus on US...the DM's and the Players of D&D. I don't much care for this constant "Tooting of their own horn" with every supplement they put out. To me it seems like WotC has taken on the role of those annoying parents who attribute all the success of their wonderkind's success at [insert sport or ability] to themselves more than their kid. Yeah, you know the type. That's WotC now. "Look how great my kid is! Aren't I an amazing Parent!? See what I have done? I am the one who really deserves the credit because without me my kid would just be so-so...sorry honey, but it's true. You should thank me for making you great! And everyone watching my kid should thank me too!".
WotC: Please stop trying to be *that* parent.
^_^
Paul L. Ming