It's not about completing games. It's about genres that you used to enjoy but you don't play them anymore these days.
Oh, yeah.
My bad.
Genre-wise, I used to love playing those city-builder or zoo-builder or themepark-builder like games.
But nowadays, whenever I try to get into one, I easily get anything up to some medium state of stable income (or whatever equivalent) and then I lose any and all interest in proceeding further. I don't even experience half of the content because I lose my will to play further. Due to that, I have stopped buying those kinds of games almost entirely.
Likewise most multiplayer PvP games like CS:GO or so. I played those a lot as a teen, but I guess at some point you just grow up and no longer feel that need of turning each game into dick length comparisons.
And you also grow out of the kind of communication that tends to come with those kinds of games
If anything MP-wise, I sometimes play co-op games with my partner nowadays, or maybe join some streamers' community games.
RTS-wise I can only second the notion that there haven't been many great offerings in recent years.
Most try to catch that elusive multiplayer RTS audience, completely forgetting that most people who played those games 15-20 years back didn't even play multiplayer or only very little.
And then they also pull stupid stunts like AoE4 launching without even a proper ladder, while also having super lackluster single player content.
I am convinced that a really good RTS could do very well financially - not on the same level as more casual games, obviously, but still very much profitable.
Northgard is a very positive recent example. Smallish team, did well financially, released lots of DLC, lots of content for SP and I think a somewhat active MP scene, too.
That's how you do it.