I know that once you max out your skills you can turn them legendary resetting them (Basically it is prestige mode for skyrim.) But does the game also get harder once you do this? I mean if the enemies don't get harder what is the point?

the point is so you can still level up.

before once all your skills hit 100, you could no longer level up. but by going into Legendary mode and resetting the skill, you can conmtinue to level up. and (Hypothetically) get enough perk points to unlock every perk

it allows you to kepe leveling past what you normally would be able to. so instead of for example hitting a cap of 40 or so where all your skills you use max out, yoou can make them legendary and experience more of the game and the higher leveled enemies.

I haven't personally tried legendary mode because on my current character I don't have any 100s yet, but I do know that your level cap basically becomes infinite and the enemies could level up with you. The amount of damage you deal will still be the same, example: if you deal 80 points of damage at 100 one-handed and make the skill legendary then get 100 again, you will still do 80 points of damage. So yes, it will get harder because you deal same amount of damage while the enemies become higher level.

Most enemies stop leveling after 50.

So it doesn't actually improve the skills at all, just turns them back to zero?

Seems pointless...

Being able to continue leveling without having to train skills you normally wouldn't use is pointless? Stop trying to remove features from my RPG please. More options, not less.

What does it achieve though??

Would have made more sense to just uncap the skills rather than reset them, Which is possible because a modder has done it...