The benefits of the microservice pattern are you can build separate teams responsible for different business logic, and they can have their own deployment schedule. You don't get either of those benefits when a b and c have to coordinate on their work-order creation business logic, and a, b, c and d all need to be deployed at the same time anytime the schema changes.

Btw some of the confusion might be what I mean by shared database. I didn't mean two services sharing a limited set of tables, using the database as a rabbitmq replacement. I meant sharing the backing database of the microservices. It sounds like we probably agree I just wasn't very clear about what I meant by sharing a database.

(Ironically I am literally using a database as a queue to share data between two services we are running in prod. I don't think of it as a microservice because it's not separate teams, it just because our monolith is hosted on a platform that doesn't support certain libraries so we had to role those libraries onto a separate platform that does support them.)