Code generation leaves a layer of abstraction between the API and the actual implementation which works great if that code generation is bug-free but if it's not, you're like... totally fucked. Most commonly people say you can read the generated code and step backwards but that's like saying you can read the compiled JavaScript and it's basically open source. That layer of abstraction is an underrated mental barrier.
Of course, code generation is still practical and I'm a lot more likely to trust a third-party writing a code generator like protobufs, OpenAPI specs, etc, but I would not trust an internal team to do so without a very good reason. I've worked on a few projects that lost hundreds of dev hours trying to maintain their code generator to avoid a tiny bit of copy/paste.
Of course, code generation is still practical and I'm a lot more likely to trust a third-party writing a code generator like protobufs, OpenAPI specs, etc, but I would not trust an internal team to do so without a very good reason. I've worked on a few projects that lost hundreds of dev hours trying to maintain their code generator to avoid a tiny bit of copy/paste.