Achievements make the game harder

When you complete an achievement, something in the game gets a little bit harder, balancing out how strong a player becomes, this would be togglable, but you could also control just how fast the game gets harder (3 tiers, one moves about as fast as a new player, second as fast as a skilled one, and third can't be kept up with, or very hard to) . Maybe some achievements don't cause the game to get harder (I can't think of any good examples)

How would it get harder though? Maybe mobs get tougher armor and weapons, maybe the night lasts longer than the day, crops could grow slower, maybe there's a mob that slowly gets more attacks (potions, uses totems, magic arrows, shield, different mob attacks)

You may be wondering, "we already have a difficulty system, why change it up?" just to clarify, there would be no removal of the previous system, just an addition to improve end-game difficulty, the problem with the last system is simply that in late game (even in hardcore difficulty), survival is too easy, this idea should solve that problem

To summarize, the more achievements you complete, the more bad is in the world, thus balancing end game difficulty.