This depends on if it's your style but I love RTS (?) And management Games. Specially ones that are long term. I can easily spend a third of a day playing cities skylines or a civ6 game, and they're all casual and slow games. Here's a list of the ones I've played:
-cities skylines: the base game is extremely enjoyable and gives you tools to make big cities and have a blast managing them. Making them either the most fucked up hellscape or paradise. But this one benefits the most from expansions, but they're really expensive so I just got it off steam unlocked. My favourite one is the university expansion as I really enjoy building a big university campus in the middle of my city.
-civ6. I've only ever played civ6, but it's amazing. I usually take it slow since I love building up my nation to be massive. I take multiple days in a single game and even if I loose I like to keep ok playing. Again, the base game is great, but it's amazing with expansions. It almost feels like a different one. But it's expensive af so pirate it lmao.
-prison architect: I've never played expansions since I got it off Xbox game pass PC, but it's so fucking fun. I can sink an entire day into building the most efficient prison possible, and you can even play as a prisoner in your own prison trying to escape. It's extremely fun and it can be as simple or complex as you let it.
Age of empires: now this can be taken as a competitive game, but I usually play long single player games as I love building a big city and destroying everyone after about 10 hours of gameplay. It can be a bit fast at times, but I usually take it slow.