So instead of using debian:11-slim as I propose, one could use a Dockerfile made for Django. But that would help very little. Django even abandoned their official Dockerfile because it brings so little to the table.

In my opinion, using a higher level Dockerfile than the bare OS is a net negative. The developer won't know how much magic it hides. Even though it just hides a few lines of code. And being higher up in the stack also means stuff will break more often and the scripts need to be updated more often.