You can still have isolation of responibilities between modules, like "this module only reads and writes to that database schema". Modules combined with appropiate glue then makes a service that is "fat" in responibilities but lean in network latencies. Code reviews that also checks that module seperation is maintained really helps.
Id go a lot further and say you should invest a ton in enforcing module boundaries automatically. Shopify's approach to writing their own package manager comes to mind - you cannot rely on code review to keep code clean. Entropy will naturally lead to boundaries broken down. If you want the separation of microservices with a network to enforce it you need robust tooling to enforce that.
In java land, I have found multi-projevt gradle builds and copious tests have gotten us pretty far without needing to resort to a custom package manager.
