You're right not all of those need to be conflated but they aren't entirely orthogonal either, uv can install/manage python installations for you and poetry can manage environments as well if you want. On top of that, you have tools like mise that are more cross cutting.

I agree that there is a really nice simplicity to requirements.txt but I've myself enjoying uv enough to just fully embrace it (and not farm out to uv pip) and as a result I now find myself in pyproject.toml land.