First, it was just a skit. It was scripted, and Shatner agreed to play along. He still appears at Star Trek conventions, frequently with Leonard Nimoy, Patrick Stewart, Avery Brooks, and other famous Trek actors.
He may have had similar feelings 20 years ago. He usually rushed in and out of conventions, not because he hated doing them, but airline travel in and out of places was such a hassle. He was professional but distant with the fans at that time. When he was doing promotional appearances for Generations, he really decided to try to understand Star Trek fandom and wrote "Get A Life!"
He really got into how fans think, and he doesn't really hold the opinion it's all a waste of his time.
So, I guess he was right after all. The "Evil Kirk" said it.