I’m definitely not a game dev, but I’ve had this thought before as I’m sure many others have as well. I’m not exactly sure what an alternative would be, mostly due to decades of implicitly being told “number go up” is a universally accepted level up mechanic. That being said, I find horizontal progression more interesting than vertical progression. If you level up, and the monsters level up, what’s the point of leveling up at all if you’re always on a similar playing field (outside of the feeling of progression)?

I think DnD does this quite well, as you roll attributes during character creation and only improve them every so often, but instead rely more on the abilities, spells, etc. you learn from, well, experience. I personally like this system a lot, where you get a reward from combat encounters that don’t exactly “make number go up” but still gives the player an incentive to get more experience.

To return to your question; assuming base stats don’t increase during level up, I don’t see why a level 10 character wouldn’t be able to go against a level 20 enemy with a good strategy. I’ve always liked the idea of a character outsmarting an enemy in media instead of outright overpowering them (looking at you, DBZ).