As Cities Skylines II still isn’t worth it (the sub has a regular thread about that, in summary: no it’s not: https://old.reddit.com/r/CitiesSkylines/comments/1ch6lup/is_cities_skylines_ii_worth_it_megathread/) which games scratch your city building itch?
Not sure if it’d quite qualify as “city builder”. I’d call it “base builder”. But since others mention them:
The above games focus on the interactions of various things you build. They have a very high degree of replayability. Dwarf Fortress has a very high bar to entry, but for all of them, you’re going to be reading wikis and spending a lot of time understanding mechanics. I think that they all give very good value for money.
Cities: Skylines (the original). It’s not bad. It’s quite expensive, if you’re going to buy a lot of the DLC – it’s a typical Paradox game, where the cost of the base game isn’t a large chunk of the overall price, where there is a lot of not-cheap DLC that really adds up. It currently has a lot of its content on sale on Steam, and even on sale, a purchase of all of it is $250. But…there’s a lot of neat stuff there. It’s one of the few relatively-modern citybuilders. It has curved roads. I don’t care that much about this – and I think that the focus on graphics was a major contributing factor to Cities: Skylines II doing poorly – but it is relatively-pretty.
Sim City 4. It’s not new, but it should still be perfectly-playable. I still don’t feel that there’s a game series that has really replaced the Sim City series.
The Tropico series. This really hasn’t changed all that much (other than Tropico 2). I don’t think I’ve played Tropico 6, but I’d probably recommend that as just being the latest in the series. It looks like they pulled the campaign from the latest, which is basically fine from my standpoint. More focus on individual characters than most city-builders. A lot of the city-builder genre feels like of Star-Trek-y, kind of a focus on creating a utopian society, so this focus on running a banana republic can be a refreshing change thematically.
Lincity-NG. Not technically the best, but it’s free and open-source, which may appeal. Focus mostly on dealing with freight congestion and achieving sustainability, which is a significant shift from most of the genre in terms of goals.
Along with your not city builder but somewhat has the same feeling as one, I’d add Factorio. The way things link together, and you essentially build roads/trains for supplies, gives a similar experience. I think there’s also a mod that adds people you have to take care of and other City-builder mechanics.