I mean monoliths specifically. If your mono repo is just storing many repos in different folders and aims to keep all that in lockstep it is a bit different.
But I think you're the first person to introduce the concept of a monolith to the conversation. How you structure your repo is an orthogonal question to how you break up your deployments, and this conversation is about the former not the latter.
A monolith that's broken up into 20 libraries in their own repos also prevents experimentation with new runtimes just as much as the monorepo version does.
