Modular monolith: the overlooked middle ground?

I've been increasingly advocating for the modular monolith pattern, especially after seeing several teams attempt premature microservice adoptions and struggle immensely with distributed complexity. It feels like a vastly overlooked middle ground. What are the best practices for truly enforcing module boundaries within a monolith, beyond just convention? Are there specific language features or build tools that help with this? How do you handle database strategies for individual modules within a single codebase? I'm trying to collect strong arguments and practical examples to guide teams towards this approach for faster initial development and easier refactoring later.