I'm not sure what you're getting at here. Mono-repo is entirely a different concept then centralized (eg: SVN) vs distributed (eg: git).
I'd also seriously question an org not using git, specifically, despite claiming "cargo cult". Literally every developer knows it, it's got a huge choice of tooling, and every service/tool (CI/CD, issue tracker, etc) has an integration. IMHO, you better have a damn good reason to be on something else to justify the headaches involved of being not git.