RimWorld raids are actually ridiculously easy to defeat.
The problem is that there are two ways to play RimWorld which will lead to very different results there.
A.) You do what "makes sense" to a normal human being dealing with a real situation.
B.) You know the algorithms and minmax.
If do A.) the game can be incredibly frustrating as you watch the colony you spent hours carefully building go down in flames despite the fact that you seemingly did nothing wrong.
In contrast, if you do B.) the game becomes so dead easy that you can't even impress other players anymore by starting alone, naked, as a tribal, on an ice sheet - with one leg!
Have you ever wondered why RimWorld likes to throw that "Imperial Deserter" quest at you right at the beginning of the game?
A.) people will think "This is silly, how could I possibly defeat an Imperial raid right at the start?"
Meanwhile B.) people are like "Sure, no problem. I can build a wodden trap corridor on day 1 which will kill the entire raid before they can even see a single of my pawns."
Also note that RimWorld raids are scaled according to colony wealth and number of pawns in the colony. Thus if you are an A.) player you are probably accidentally signing your own death sentence by e.g building fancy bed rooms for your pawns. Or givign your craftspeople chairs to sit on while they work..
I think the game needs to be rebalanced somehow to make it a less frutstating experience for A.) players. Cheesey tactics like kill boxes which exploit the stupidity of the AI, and seemingly non-sensical decisions like not letting your colonists have chairs, should only be required at the highest difficulty level IMO.