It however shifts a lot of the complexity of building the application to the distro maintainer, or a software maintainer has to prioritize for which distribution they choose to build and maintain a package, because supporting them all is a nightmare and an ever shifting moving target. And it's not just a distribution problem, it's even a distribution version/release problem.

Look at the hoops you sometimes have to jump through or hacks you have to apply to make something work on Nix, just because there is no standardization or build processes assume library locations etc. And if you then raise an issue with the software maintainer - the response is often "but we don't support Nix". And if they're not Nix/Nixos users, can you blame them?

If you've ever had to compile a modern/recent software package for an old distro (I've had to do this for old RH distro's on servers which due to regulations could not be upgraded) - you're in a world of pain. And both distro and software maintainers will say "not my problem, we don't support this" - and I fully understand their stance on that, because it is far from straight forward, and only serves a limited audience.