The individual code bases of a microservice might not involve spaghetti code, but the interconnections certain can. I'm looking at a diagram of the service I work on, with seven components (written in three languages), five databases, 25 internal connections, two external interfaces, and three connections to outside databases, all cross-wired (via 6 connections) with a similar setup geographically elsewhere in case we need to cut over. And that's the simplified diagram, not showing the number of individual instances of each component running.
There is clear separation of concerns among all the components, but it's the interconnections between them that take a while to pick up on.
Fair; I should have been more explicit - your code can't fall into spaghetti (since the services are so small). Of course, you're just moving that complexity into the infrastructure, where, yeah, you still have the same complexity and the same pressures.
There is clear separation of concerns among all the components, but it's the interconnections between them that take a while to pick up on.