Gonna say it again, but Rimworld is host to numerous
cursed game design problems, the least of which being the conflict between increasing raid difficulty and the players expectations of building a defensive, yet productive colony.
When Tynan elected for DF style digging (every tile is mineable) paired with a simplistic A.I., coupled with a 2-d map with NO vanilla moats, or 'real' walls, you end up with a really shitty tower defense game. Sure, there is a sense of meaning given to your pawns and turrets since you had to harvest the food to feed the workers who mined the ore to craft the turret - but all that meaning is thrown out the door when you make those defenses practically irrelevant, since the only true way to defend is by playing the meta-game of killboxes and so forth.
Difficulty levels are somewhat of a cop-out, since I would argue the game has no comfortable middle ground between "boring colony simulator" and "death by infinite meat puppets".
Also, lets be real - when you borrow so much from another game, and find yourself riding a wave of newfound popularity, there might be a slight chance you don't know how to follow up. Tynan also never struck me as the amiable dev, you know, the kind who blogs about cool or interesting upcoming features, or works with the community (see Cogmind, Starsector, and well DF blogs for what I mean. That kind of writing is genuine and trustworthy). Tynan is very much a businessman, and Rimworld is his property. This relationship does not make for interesting games.