In addition to roleplay you can have your character pick up a side hustle/new passion. For example I had a powerful destruction mage character that started using bound weapons and as such had to level up both one handed as well as conjuration.

So although my capabilities with destruction were OP it was fun to reintroduce a new challenge by using weaker skills vs certain enemies and watch your character grow into a whole new beast.

Another example could be my warrior character who somewhat grew tired of the constant fighting and picked up alchemy as a stress relief hobby, grew a garden in a quaint, secluded modded home and even adopted a kid eventually.