Nobody cared for good reason. I'm going to break down mine.
Yes everyone noticed it. Everyone also noticed that Geralt gave up on the fantasy of a family, him living a normal life, with Shani and Alvin the moment shit came down on his head. The Shani arc concluded in Witcher 1. Same thing happened with the Triss arc, but in her case, she was around after her arc concluded, allowing Geralt and her to rekindle a sexual relationship (no relation to the romance arcs in TW1 which were explicitly about the family stuff) and according to your choices in TW2 she can either be lover, on-off fuck buddy, or friendzoned.
I don't care about Yaevinn or Siegfried, so I can't answer as to the quality of their portrayal in TW2, but from what I saw of the ending, Yaevin was an airhead whose head was full of dreams (I believe Iorveth said as much), so it's no surprise he's not in TW2, since the character sucked, and if I had the option, I would not have put it in.
Siegfried was reduced to a cameo... again, do not care. The order is fully under Radovid's thumb now, he is their grand master in all but name. What did you expect would happen when Siegfried met Geralt? They'd share beer, smoke stuff and reminisce? The guy is a figurehead without any political backing and is now on Radovid's leash. How would he impact events?
If you played the games you'd know that Witcher 1 is a closed story, much like the short stories Sapkowski wrote. There is a definite beginning, an end etc, and CDPR made the game for fans of the books. It was only in TW2 that they began to stretch their own legs, in a creative sense, and it can be seen in the writing. A lot of it is... problematic, from writing, quest design, to camera work. I wish I could have helped ...but that is irrelevant.
Also, if you read that interview that popped up a while ago, about 40% of TW2 was axed because reasons. That is partly why choices did not impact events much in the second game.
Lastly, and to sum up, you are correct about the choices not affecting much but it doesn't matter because the plots of the first game are closed ones, even if you couldn't see it. Also, game was axed removing a lot of stuff. I saw this and decided, along with many others, to give them a pass. What you decide is your concern.