It is simple really. The most "avid Skyrim complainers" are long time TES fans who are willing to really put the game through its paces because they want the series to be improved.
I don't really like Dragon Age: Origins that much because it is not an open world "do what you want game". After playing Oblivion for more than 500 hours, I played that DA:O for like five hours, but it was not for me, so I took out DA:O and put Oblivion back in for another 500 plus hours. Did I join a DA:O forum to complain about it? No. Not worth my time to complain about a game that is just not my cup of tea.
Skyrim, however, is a TES game, so here I am complaining about it. Now granted, I still enjoy Skyrim quite a bit, maybe even more than Oblivion or Morrowind, so that is part of why I have put several hundred hours into Skyrim -- I enjoy it, but there is still a ton of stuff about Skyrim I would like to see changed and improved.
I'd bet that most of the "avid Skyrim complainers" are like me and enjoy the game despite its flaws but want to see the series improved. And even those "avid Skyrim complainers" who don't enjoy playing Skyrim that much probably have played other TES games that they do enjoy and are at least willing to give Skyrim a good try before condemning it.
Remember, there are lots of folks here who have put way more than 1,000 hours in Oblivion or Morrowind (or both) so for folks like that, 100 hours in Skyrim is a drop in the bucket.



