It gets much more of a challenge once you go past level 8/9 I'd say, that's when most managers are active.

I enjoy each season as every new league/cup/CL you get seeded into brings a new challenge, couple that with the excitement of developing existing players and finding new ones, it's enough for me.

The game does have a large social aspect to it though, try and get some of your friends into the game, or start a team showcase like other members?