Most companies will never have a monorepo at the level of these bigger companies. So I personally don't think most people need to worry about the limitations of github/lab as platforms.

However if you happen to be having those kinds of issues, I think looking at what the big companies are doing and/or starting to split things up makes sense.

There's also alternatives with custom ci jobs within non GitHub/lab within the git universe that may help out with those sorts of operations. I know actions still feel very beta in some toolsets so it may be easier/more useful to run your own arch. I've been enjoying forgeo/gitea for example, but it's not like you can't do the same with girlab runners or GitHub enterprise. Depends on use case.