I wouldn't say many people, just some. He's a classic gamer that was around for the first GTA. Obviously he's going to be bored with the series after the 5th instalment. It took me something like 3 years to beat GTA 4. I don't see that as a bad game, just that I outgrew it. It no longer holds that awe for me. Drive around, review the tech, have a little fun, move on.
I think he feels the same way, but he's also confused. Anyone who knows GTA knows there is no story. Whatever dialog they have in there is just filler. GTA has always been just a quick and dirty action game. It's a playground, a way for you to release that inner rage and become the violent human you always wanted to be, but were to afraid to get shot or go to prison He's just tiered of the series. That's understandable, but millions of other gamers still dig it. In a lot of ways, Rockstar has an obligation to continue the saga. Not only was the revenue earned on this project evidence the theme is alive and well, but it's like their trademark. This is who they are and what they do. And while I will not pick up GTA 5, 6, 7, etc, I don't discount there are others out there that do want it.
As for the gamer trash talk, well you just have to think that's the generation of kids we're raising. You think it's bad now, wait until these kids grow up and start running the country