I agree that there are problems when laying multiple build systems on top of one another, and I see that often as a user of nix (it's also bad with rust projects that use cargo, and though there are a variety of options folks have written they all have tradeoffs).

To some extent, the issue here is caused by just what I was discussing above: Nix derivations can't dynamically add additional derivations (ie: build steps not being able to dynamically add additional build steps makes things non-optimal).

I am hopeful that Nix's work on dynamic derivations will improve the situation for nix (with respect to bazel, cargo, and others) over time, and I am hopeful that other build systems will recognize how useful dynamically adding build steps can be.