Someone really needs to develop a lightweight VM container that we can stuff software in. Like, you know how you can buy DOS games on steam, and it just gives you dosbox preconfigured to play the game?

That, but for all software on all OSes

@foone sounds like unikernel

sure, its not quite what you want, but I think it gets the idea across
https://unikraft.org/
Unikraft is a fast, secure and open-source Unikernel Development Kit.

Unikraft is a fast, secure and open-source Unikernel Development Kit which enables you to build custom, minimal, immutable ultra-lightweight unikernel virtual machines quickly and easily.

Unikraft: A fast, secure and open-source Unikernel Development Kit.