It’s real deep in content I bet if this game was released today half of the content would’ve been dlc. Here’s a list of things you can do In the game
1.become the arch mage
2.become a vampire
3.become a werewolf
4.become a assassin
5.become a thief
6.become a companion
7.become a necromancer
8.become a legate for the empire
9.join the stormcloak rebellion fight against the empire
10.join the Dawn guard vampire hunters
11.become the strongest Dragonborn.
With mods this list would become nearly endless
However the problem with the game isn’t anything I’ve listed so far. It’s that there are still glitches that have not been patched and so you’d need to use mods to fix them luckily these glitches are not game breaking.