Still, that's a limitation of the specific tools and the way you're using them, not a fundamental problem with monolithic repositories.

You're running into problems because you have multiple people all trying to push to the same branch, and Git errs on the side of extreme caution rather than creating a merge that you didn't specifically request. If you use merge requests instead, as supported by Github/Gitlab, you don't get blocked by other people's commits.

(Actual merge conflicts are an orthogonal problem. They'll happen whenever you have multiple people editing the same code, regardless of what VCS you use or how it's organized.)

The Linux kernel example is a bit of a tricky one. Yes, kernel.org hosts a lot of repos, but they're all different versions of the same codebase. They have a common commit ancestry, and commits get merged from one to another. So they're not really separate modules in the sense that we're talking about; they're more like namespaces that each contain a set of branches.