Theres also Vivaland which is going to offer multiplayer IIRC but I dont think it will be that strong in the simulation aspect but we will see. So there is finally some competition in the genre vs The Sims.
Part of me thinks this decision was down to the fact The Sims is still going strong. Paradox spun up Cities: Skylines and had success due mainly to SimCity imploding itself.
They were perhaps not looking to compete and gambling on EA ruining one of their own franchises again, in order to fill the niche in the market.
Which game are you thinking about with X:COM? I did see Millennia, but either it was marketed badly, or I just managed to miss the hype machine pre-release. It just seemed to suddenly spring up with swathes of middling reviews.
I'm kind of a casual Paradox fan, but don't really stray from their PDS releases usually.
I was quite interested on that and downloaded it on Game Pass, but never found time to try it. It seems that game caused them to part ways with Harebrained Schemes, which is a shame. I enjoyed Battletech that was the same sort of turn based combat thing.