I suppose. I guess after ten years of WotC producing largely the same format every single time, expecting this book to be different is a bit... strange? Sure the content is different, but, as far as format goes, how is Ravenloft or Tasha's any different from SCAG or Xanathar's?
I guess I just don't understand why anyone would expect anything different. WotC's been pretty open and clear about what's in the books, to the point of publicly playtesting large amounts of the material beforehand. Turning around and complaining that they don't have new rule modules for things they've never even mentioned (like, say, Armor as DR as an example) isn't really paying attention.
I don't think many expect to see a bunch of rules that drastically change the fluff or crunch of D&D.
But it is completely in someone's right to complain that the official publisher doesn't provide something in any way popular that unofficial publishers are providing. Niche is a matter of degrees and not everything WOTC created for 5e was begged for. It's irrational to expect something when the turn had been made. However one can complain about the turn. Especially if another direction or option was once hinted at.
I don't expect big rule modules from WOTC at this point. That's why I predicted a downturn in 2 years in the first place.