I'm level 64, on top of my server, been here since late last year. At the point what you called the end game. Now you probably wonder why I even care enough to rant here over my failures.
I too face the same teams all the time and I know everyone. Sometimes the level doesn't go up, etc, you who are this high too know. Among the same familiar teams, there are the ones who buy a lot of tokens, and win pretty much all the tournaments every season, while I do not buy. I can get myself a 7 star team, they can get 8. I'm always in the league where those toughest managers are.
I could start again and succeed better, but I've won all the tournaments anyway, most of them several times, and winning trophies itself doesn't matter much. That's why I also don't stay in the same level on purpose. I want to beat those token buyers who dominate the game, that's what keeps me carrying on. I've won them many times in single matches but rarely in the long run. I've never won them in league, I've been second at best. I've never won them in Champions League, I've lost the final at best. Last season, I finally won the Cup.
So you see, I've got an clear objective. I don't want to just win, there are people who I want to win. That's what keeps me playing.