I think one version is important for a healty polyrepo as well. You have to set lines where you say no new features unless you are all up to date. You can allow bug fix only releases to stay behind, but if you write a new feture it must be against the current latest of everything.

Otherwise you are doomed because there are so many different versions of everything in use. Some day a zero-day issue will hit all your projects as the same time and you will need months to get each in use version fixed.