In this case, I'd say it's the opposite: monorepo as an approach works amazingly well for small teams all the ways up to huge orgs (with the right tooling to support it).

The difference is that past a certain level of complexity, the org will most certainly need specialized tooling to support massive codebases to make CI/CD (build, test, deploy, etc.) times sane.

On the other hand, multi-repos may work for massive orgs, but is always going to add friction for small orgs.