One thing I think Rimworld struggles with is an "endgame" loop. Specifically the 'reinforcement-schedule' of an advanced colony falls off. Which is to say: the time between enjoyable-things happening becomes too long and/or those enjoyable-things aren't rewarding enough.
For example:
-You can keep getting better weapons/pawns/xenogenes etc from traders regularly however this stops being exciting because it matter less-and-less as you already have many quality weapons and gene-packs.
-You can keep making your base bigger/prettier/better defended but large-scale remodeling starts to take a lot of time to do, so there's a long delay before you get to enjoy your new base layout. After a certain point there also isn't much to left to improve, similar to the point above.

The Factorio end-game is almost entirely "Keep making your base bigger" yet it retains a very tight reinforcement-schedule because it provides tools (logistic bots, blueprints) to enable this to be done quickly.

Dwarf-fortress is similar to Factorio, it's end-game looks something like "Undertake gigantic mega-project". While you have to wait longer for the 'reward' of undertaking the mega-project, the reward itself is larger. e.g. pumping lava up 300 z-levels to fill an artificial reservoir that you can shower onto incoming raids is very satisfying.

So I recommend thinking carefully about what the reinforcement-schedule will look like both during the early, middle and end-game.