It's a very poor system, I agree, but there's ways to sort of mitigate it. Takes work on your part but some of these strategies have helped me make CM more challenging this year (though I'm playing on PS5; if you're not, YMMV).
- Switch between team sheets to ensure players don't go past ~50 sharpness
- Get angry with your team/players in press conferences and player conversations to keep their morale more level and avoid boosts.
- Avoid filling your team with youth. Focus on a more realistic balance so that you don't have players constantly growing
- Use a slider set that makes the game as challenging as possible. Poorer results equals less growth.
- Use high injury frequency to disrupt your players from growing consistently
- Focus your financial resources on defense. The game is oriented toward attacking play, so you don't need OP attacking players. But OP defenders aren't a big deal.
- Like the above, focus player training primarily on the defensive stats (even with attackers). Limits OP attackers.
One of the biggest challenges with CM is actually creating a challenging experience lol. This is what I've done this year and it helps, but yeah, it's way too easy to build an OP team.