I'm sure there are some good mods, but I never understand this attitude that vanilla isn't good.
Resume real quick since I feel lot of people get touchy every time I critic this game:
- Too much RNG handling. Skyrim is basically a random stuff generator that feels awfull as you want to explore, with rewards that only truly shines as you get high level
- Too much randomness on enemy scalling. Some dungeons have 1 static enemy sure, but mostly are random generated taking into account your level
- Almost basically every mechanic in this game doesn't work as it should. Magika regen get heavy penalty when you enter combat for instance, but that doesn't applies to enemies which make enemies mages looks like have infinite magika(rendering lightning spell useless)
- Most of enemies have hidden skills and better scalling just to break the rules themselves created
- Too heavy in favor of frost resistance. Because the way Skyrim is structure to have good amount of Nords, the game disfavors frost builds thanks to a huge cast of enemies naturally resistant to it
- Bugs(alot) that impedes some random encounters to even activated or work properly
- My favorite: imbalance on spells, with non sensical spell costs that even perks can't handle unless you use the 100% reduction cost trick
And so on, I could keep here all day telling all that is wrong with this game and wouldn't make a difference.