I think you're being too reductive. Besides the fact that software packages produced by GNU are historically significant (without GNU there is no OSI or even linux), "viral licensing" is a not a good way to describe copyleft (what would you say about Creative Commons then?) and different forms of copyleft exist.

The GNU Project is not just software, it's a philosophy and political stance about people's right to control their computing. The ultimate aim of the project is to produce a Fully free operating system. People are "loyal" (if we accept that wording) to GNU because they believe in the idea of a completely free operating system that only uses free software.

I'm not here to antagonize you, have whatever personal (albeit critical) opinions about GNU or the FSF or whatever group in the FOSS community as you wish (believe me, I have my own hot takes). I just wanted to point out why the GNU Project is significant if not fundamental to the entire Free software ideology and misconceptions about it.