Rimworld is simplified in some ways in that you have only one z level, and it comes with more QoL features.

Rimworld is a lot easier than DF to learn, and more intuitive.

And generally, you have fewer rimworld pawns than DF dwarves, so managing them is easier.

I for one love both games. Sometimes I want the simplicity of Rimworld. Other times I crave the endless complexity of DF and all the possibilities it brings.