Open world RPG always a good time for me. Mods are the reason to continue playing it now. Spend more time modding than actually playing, but once you finally finish modding then a full playthrough is a great experience.
Mods are the only reason to really play any Bethesda game. The engine they're built in is outdated with simple gameplay mechanics so you have to mod them to get any sort of satisfying gameplay. The story lines they come up with only get you so far and considering the age of the game at this point without graphical mods it's going to look extremely dated.
Not the base game itself, but the almost unlimited possibilities that are created with modding. It feels like you are able to create your ideal fantasy if you're willing to put in the work
I wanted to play Skyrim since its release, but couldn't commit the 300 hours it would take me (I want to loot everything that's not bolted down and collect all books).
Today I still want to play SKyrim, still can't commit to 300 hours
The fact that there's so many mods and that you can turn the game into whatever you want.
The regular unmodded game is not that great in my opinion, it was pretty aged graphically when it first released too. It feels like this can be said for all Bethesda games though.
It was a good open world RPG when it came out, with the lore of TES behind it. The modding community prolonged its lifespan far beyond what is normally possible, but when a game requires the installation of hundreds of mods to be playable, you know it's time to say goodbye. People still playing it today are doing it mostly out of nostalgia (IMHO). The reality is that TES6 is at least 5 years late and if it doesn't release soon, the franchise will die. And the expectations for that game are so high, that it is highly unlikely to meet them anyway, which is another disaster for Bethesda waiting to happen.