> Compiling most things is decidedly nontrivial.

I've spent the past five years building a lot of things from source. I agree that there are definitely a lot of things that it's nontrivial for. However, I've found that the hardest part is satisfying dependencies. Once dependencies are satisfied, building is usually really easy. And the software that isn't easy to build after satisfying dependencies is usually not worth building in the first place.

Of course, that's just my experience as a C++ developer.

Gentoo can do prefixed installs, I'm reasonably certain alpine can as well. If you're on debian you can always just make a chroot with debootstrap.