There is foundation to these complaints, though.
The games take very marginal steps forward while taking large steps back in areas that people loved from the previous games. Daggerfall had an unimaginably huge world, tons of unique loot, unique characters and tons of quests since it was mostly randomly generated. Then Morrowind comes along with core game mechanics that are largely the same, only in a smaller, hand-crafted world. I wasn't around when Daggerfall launched, but I went back to play it after I played Morrowind. There's literally thousands of hours of gameplay packed into that game, it's ridiculously huge but if you can look past the graphics, it's just as much of a game as Morrowind.
Then Oblivion comes out and is in my opinion a step back from Morrowind in mostly every way besides visually. The storytelling, graphics and combat got marginally better again, but the world wasn't nearly as rich and there was a lot less role playing freedom compared to Morrowind. Oblivion isn't as bad as say DMC 1 to DMC 2, but it was subpar enough that I'll probably never play it again.
Morrowind struck the best balance of a unique, hand crafted world and role-playing freedom in a modern game. That freedom is what people play these games for, and as good as Skyrim is sounding right now, we're still not sure that it manages to recreate that freedom.