I’m not aware of much else that fulfills this niche well - conda seems very very tied to precisely tested version combinations, and (from what I remember - tried and had problems) nix seems to want root/system level daemons.
[1]: http://pkgsrc.org/
I'm curious why you feel this way.
Hello. Conda core contributor here. Do you have any more details? Would love to help.
We try to keep version constraints among dependencies as loose as possible. We do actively patch dependency metadata over time, putting upper version bounds on dependencies when incompatibilities eventually arise.
A word of warning, however: Homebrew 2.0 removes your old formula from the Cellar when upgrading. If you want to disable this you must set HOMEBREW_NO_INSTALL_CLEANUP in your environment if you want to hold on to those older versions.