It felt like they were trying to make an MMO be a table-top game at the time when WoW was at the height of its popularity (that WotLK nostalgia). Its not that it was overly bad, it was a square peg, round hole situation.
These days I feel like 5E has no teeth, very good intro but beyond the first few campaigns and the endless art books its mechanically uninteresting. Pathfinder 2e has been what most of my games have converted to.
Painting in broad strokes here as its been over a decade since D&D v4 and WoWs high-water mark, I think people call it that because of several factors, not all of them in the game design of v4.
D&D v4 to me will always be the MMO version because it was a product of its time, and also WotC scrapped pretty quickly, relativly speaking.