One of my professors at UT Dallas has a book that argues that districts in fact should be partisan. It's been a few years but the logic is something like if you've got a 50-50 district, you're gonna end up with 50% of the people in the district unhappy. Where as if you intentionally designed districts to be like like 90-10 (or whatever possible), more people are happy.

Not sure if I believe him, but it's interesting.

Redistricting and Representation: Why Competitive Elections are Bad for America

https://www.amazon.com/Redistricting-Representation-Competit...