Well, they're repetitive now, but back in the very beginning, not really. Personally, I only really got sick of it once it got to gen 3, but by then, the original writer was gone. Of course, I like repetition more than most, I played the games a ridiculous amount of times and rewatched the anime every chance I got, back in the day. Still, in the beginning, it was a fresh new thing, it wasn't formulaic and overdone yet, they still had original ideas (and could get away with doing them because the franchise wasn't as tightly controlled and conservative in the bad sense) and a lot of old episodes are very memorable. It was still this mysterious new world, not a time loop with no lasting character development, that lasts until it's not profitable enough to keep it going.

I think someone could maybe argue with the gen 2 portion already being kinda repetitive (I haven't seen it in a long time, and I don't remember as much of it), though even then, the ending of that was satisfying and if it ended there, it would have been a very good show overall. And even if it was repetitive, it was their first time being repetitive, and to me at least, it was still exciting, because it was their first time doing a new region, with new pokemon, and it was an actual continuation of the story, while following seasons feel a lot more detached, like rebooting a story that was already basically over, with the Satoshi and Shigeru rivalry, that was set up in the very first episode, being concluded. There wasn't much left to do. Of course, Satoshi in particular still hadn't achieved his goal, so maybe there could have been one more season, but from there, the writers changed, and no progress was made, for so long that I can't imagine many people not dropping the show at some point or another.

Anyway, I still ended up watching most of the gen 3 anime. Pretty weak. And from there, I only watched parts of it, that happened to be the cool parts of the gen 4 anime, and that was it. Also, I watched the movies up to gen 4 as well, because they were self-contained, so why not?