Having been down the route of repos for every service I would always choose monorepo in the future. I could see separate repos for libraries. There is just too much overhead trying to manage multiple repos. With a single repo it's possible to build a package that represents all of your software vs being forced to version everything. Tasks almost always touch multiple services unless you are so big you have a team per service.
I don't agree with having libraries in their own repositories. For us one of the biggest costs to fixing bugs in libraries particularly was having to then update all dependent projects with the new version. By moving our libraries into a monorepo alongside all the consuming projects we got away from that busywork. It really streamlined things for us.
