I don't recall much in the way of backlash in response to Heavensward. It was heavily praised and most of the drama, I recall, was based around the long delay between 3.0 and 3.1.

Stormblood was a mixed bag though despite some finding it to be 'boring' it wasn't nearly as divisive as Endwalker proved to be. In no small part, I suspect, because it didn't try to justify the genocide of the Ala Mhigans or Domans. Meanwhile we have Endwalker which writes off a bunch of men, women and children and tries to present their genocide as the actions of a 'good person'. Weird!

Shadowbringers wasn't necessarily what people expected at the time, though it was widely praised for the most part.

Certainly, you can go back through any past expansion and find negative reactions but there's something of a perfect storm at play these days. Not only are we missing a planned expansion, the story - supposedly the bulk of focus in the game - has been compromised on many fronts. Then we add in tone deaf statements from the lead developer such as 'go play ultimate' in response to years worth of healer concerns, the prolonged mismanagement of player housing, the hyper focus on pleasing the Twitter sphere, Hrothgar hairstyles and various other factors...well, it becomes a bit too much even for many veteran players.