The core idea of SOAP was good. The ability to generate client and server code stubs from a single declarative file was great. I worked with SOAP extensively in early 2000s.

The problem that killed SOAP, to my mind, was growing complexity that eventually started to outweigh the benefits of the protocol. Not every implementation supported every new complication that, say, MS kept inventing, it hurt interoperability.

I think a modern sort-of-replacement for the SOAP's use case is GRPC. It eschews the heavyweight XML and tries to keep things simple, while staying reasonably typesafe, declarative, discoverable, and extendable.