I did not forget about it, I never heard of it
I wasn’t paying attention to TTRPGs at the time, drifted out during 2e and back in during 5e. So no first hand knowledge, but WotC designing in an ivory tower pretty much sounded like the consensus in the retellings I have seen since
Well then, let me tell you the tale of Darth Wyvern the Golden.
4e was originally going to have a lot more flavor and setting information. They released an early preview showing a Wizard feat, "Golden Wyvern Adept". The feat was mechanically identical to the eventual Spell Accuracy feat we got in the actual 4e PHB1, which functionally works like the 5e Sorcerer metamagic "Careful Spell" (but it scales off your Wis mod, not Cha, and could be used anytime, no resource cost.) It came with various fluff bits talking about the Golden Wyvern order and its Adepts. None of the fluff was
mandatory, it was just pre-written, so that the game would have a flavor and direction to start with.
This precipitated an absolute
firestorm, because how DARE the books DEMAND that every GM's world absolutely must have Golden Wyverns in it, and an order of Adepts named after it that practiced certain types of techniques! That was so horrendously offensive, it kicked off an
incredible wave of outrage. So WotC listened. This was before the books were ready to be printed, so they adjusted. They removed all of the flavorful names and gave things clean, dry, no-fluff titles so that every group could invent their own flavor. They reduced the presentation of fluff on powers to just a single line of generic descriptive text, so that people could get a loose idea of the designers' intent, but not feel in any way restricted by that intent. They focused their designs on being effective mechanics, and trusted GMs to specify the flavor and world-building, because that is what people told them they wanted.
And then what was 4e trashed for? Dry, mechanical descriptions and design. Books with no flavor, descriptions that were "anemic", everything sooooo generic.
It was
quite literally listening to feedback, responding to a firestorm of criticism,
and then getting a new one for heeding the first!
TL;DR: The designers tried to include flavor. They were told, loudly and angrily, ”HOW
DARE YOU FORCEFEED US FLAVOR?!” Then, when they published books that avoided any suggestion of forcefeeding anyone flavor...they were told, loudly and angrily, ”WHERE'S THE FLAVOR?!?!?!"
WotC could literally do no right. It wasn't possible. Include flavor and you're ramming it down GMs' throats. Exclude it and you're producing a dry technical manual rather than a lovingly-illumined manuscript.