Apart from semi standard bug fix and texture mods.

Try the ordinator mod for a complete overhaul of skill trees to be a lot more interesting. It also makes playing a caster a lot more interesting compared to the vanilla experience. You probably also want the uncapper mod to customize the amount of perks you get per level.

Personally I also use material chest mods that are basically cheats to level crafting skills, I'm not interested in grinding them out multiple times. Up to you if you want to use them to gear yourself as well or not.

If you want the game to feel truly different, you need to change your play style as well. Playing a dual wielding berserker is a lot different than a stealth archer.

Nexus now supports modpacks too. Check out their collections page if you want to browse some curated mod collections.

I play too much Skyrim (between the various copies I've owned, I have ~3.5k hours) and one of the ways I keep it repayable is by using the Enaisiaion overhauls that another commenter mentioned.

They're made to be largely "vanilla+" type mods, but they overhaul nearly everything. Races, perks, standing stones, the magic system, werewolves & vampires, and enchantments. He also has one that adds a faith system where you can worship the various deities of Tamriel and I think that one is a must have at this point.