It seems like you like games with a lot of replayability, as well as games that make you think a bit. I’m a bit of the opposite (I like shorter, unique experiences), but I also like games that make me think. So here are a few that I’ve enjoyed that I think fit the bill:

• deck-building roguelikes, like Slay the Spire, Balatro, etc; you can get a lot of hours in it, they generally don’t have DLC, and they’re more on the “thinking” vs “combat” end of the roguelike spectrum
• Planet Coaster or Parkitect - theme park themed “city builder”; Planet Coaster is a bit of a DLC-fest, but Parkitect only has 2 (and a soundtrack); look around the various “tycoon” games if you like the genre, they can have good replayability
• "coding" games - Human Resource Machine, Opus Magnum, etc; these have poor replayability (mostly just optimizing solutions), but there’s a lot of thinking and you can get a lot of hours out of it if you don’t look up guides; they’re not for everyone, but if they are, they’re very satisfying
• Dwarf Fortress - the management game, and perhaps the best in the world at replayability; the Steam version is a huge upgrade, but you can also get the classic version for free, though do be aware that the learning curve is a lot higher than the Steam version
• Sid Meier’s Pirates - old game, but I get a lot of hours in it and find it absolutely fantastic; this is more combat than thinking, but it’s more thinking than something like Mount and Blade (combat is relatively slow)
• Tropico series - they do have DLC, but you can frequently find a bundle on Humble Bundle or Fanatical or something with all the DLC included for the older games; not as sandbox-y as Cities Skylines, but still largely in that vein

That said, I want to echo what others have said and to recommend branching out. There are tons of great indie games that aren’t a total ripoff in a variety of genres, so look around for bundles or something to find something new to try.