Guix doesn't prevent you from using proprietary software. It gives you all the tools you need to use package modules published by other people, or to package them yourself. This is free software after all: you have the freedom to use Guix for any purpose including the installation of non-free software.

I'm not just saying this to make a nitpicking point: Guix makes it easier to, say, build a custom kernel using the same reliable and hackable mechanisms Guix uses for Linux libre.

It's just that the Guix project itself won't recommend projects that extend Guix with package definitions for non-free software, nor will it include said packages by default.

Guix is still a general purpose operating system running on a general purpose computer. You should be able to run any software on it that is GNU or Linux compatible.

If you don't want to go through the pain of installing it outside of a package manager, that's fine, but that's not "locking you out", it's putting the blame where it belongs: the proprietary ISV.