We do not version our services in that sense. It's a monorepo after all.
We do have microservices.
We use kubernetes.
Deployment is a breeze. Only services with changes are actually deployed.
We do hourly deploys to production.
None of the issues you describe apply here and the monorepo works awesomely for us. This is a SaaS situation where all services making up that SaaS solution and that we host are in that monorepo.
YMMV if you are in a different situation such as having to ship versioned software for customers to self host/install for example. Our accompanying software that is usable in conjunction with the SaaS solution is not part of that Monorepo and each of those are versioned and deployed to various external marketplaces.