Have you considered Enderal? It’s a total conversion mod for Skyrim on steam, so the bones of it are the simpler Skyrim systems- but it overhauls everything and has excellent world building and quests to boot. A full mage playthrough/build is very fun/rewarding. Just understand that it is NOT Skyrim. It looks like it sometimes, and there’s definitely still that Bethesda jank, but it’s its own beast.
Yes, the total conversion package makes it self-contained in the steam library/store. It just checks that you own a legit copy of Skyrim to run it. It has its own steam page even, couldn’t be easier. Plus it’s free (assuming you own any edition of Skyrim) so it’s hard to pass up with so little risk aside from your time.