Don't agree whatsoever that improving the personal interactions with core characters is any less important than say characterising Eredin better. Improving the narrative of Triss/Geralt/Yen i would consider of high importance, more so than tinkering with the conclusion. How is asking for improved Triss content fanservice but Eredin not fanservice. Throwing around nonsense terms because other people have different priorities isn't helpful.
I am not saying the Triss complainers are wrong. I can see why you would want more of her in the game but I think people aren´t focusing on bigger problems with the narrative.
At least Triss is utilized in the game to some extent, at least she has quests and dialogue and stuff, at least you can romance her and get your happy ending, at least she is still a good character. Maybe there needs to be more of that, ok, but by comparison Eredin is the main antagonist of the game and he has like 12 lines of dialogue and one shitty bossfight.
I just think the game has much bigger narrative problems than the Triss situation. And I think it would be better to improve an aspect of the game that affects everyone, rather than an aspect that just affects some. What exactly did Ciri do in the ending? Why is Eredin a complete joke character? These are the kind of things that have an impact on everyone who plays the game, rather than just people who chose to romance Triss, and should be addressed. Of course this is all assuming any of this stuff ever gets addressed and there aren´t enough resources/time to go around toward fixing everything, and I understand thats a BIG if.
I also think the lack of Iorveth/Saskia is irritating, and I really want to see them added to the full game, but again I feel that things like these are minor issues compared to the lack of Wild Hunt who are barely in the game despite supposedly being the primary threat in the story. For a game subtitled Wild Hunt, you would expect to see a bit more out of the Wild Hunt.