I still don't see how it really helps. For organizational concerns it may be easier to say that a team is responsible for a (micro)service than for a library, but it doesn't have to be easier. If they change their API all users will suffer anyway. It doesn't have to help much with scaling either. If the service/library is the thing that uses most of the cpu it will still help to add more servers with everything on them. Microservices actually may cause bigger lag since the network connections may take time (app calls service 1 which calls service 2 etc). If they all were libraries on the same server the calls would be much faster.

You do get an opportunity to monitor each service easier if they live on separate machines (or just separate processes). If you want that with libraries you need to add monitoring code to all libraries and then collect data from them to see where the bottlenecks are. You might also need to develop new tools to configure things like pool-sizes and cache-sizes for each library. For example saying that you should have 5 threads (or handlers) handling mail-messaging and 20 threads/handlers handling calculations. You might also want to be able to change theese configurations in a live system. I think a lot of applications misses this monitoring and configuration part and then gets into problem because of that. And of course microservices helps with using different languages for different parts, even though most organizations I've seen seem to mandate a specific language anyway.