> Our server models are exactly the same as the DTOs we would write, so I just serialized those, instead of writing all the boilerplate, we can write DTOs as needed later if needed

I worked on a system that used the protobuf types generated for communicating between services everywhere. There was absolutely nothing in any of the components of the system that didn't depend directly on the generated protobuf code. What made it even worse is that a backend system we called had multiple endpoints that used the same name for similar but slightly different things, so there wasn't, e.g. just a single Passenger type, but a bunch of different Passenger types across various packages.