Hard not to have major WSDL flashbacks in the OpenAPI project I have running right now. Between the lack of support for the latest OpenAPI to generated documentation in Sphinx, custom attributes needed for AWS API Gateway deployment, and the general grossness of adding the OPTIONS requests for CORS access, nothing has worked as easily as I would have thought it would. Especially given so much of the hype.
Worse, too many of the client generation libraries all look to be abandoned. With no real indication for me to know which would have a good future.
I consume WSDLs and produce OpenAPI very regularly and you're very right that we've reinvented the wheel. On the bright side, REST APIs are much easier to work with ad hoc and Open API (not sure if this is really because of the format or we just care more now) often has better associated docs.
The single dumbest thing we on a team did on a project I used to work on was use the AWS API Gateway. I have my problems with OpenAPI itself, but API Gateway itself is a half-assed mess. If we'd been able to wait a little longer, the lambda serving API requests could've just gotten the HTTP requests directly without that useless heap getting in the way.
It's a shame about the tooling. It seems like maybe lack of corporate sponsorship is a problem. I know that many companies use open API internally, but of course are never willing to actually contribute or fund the tools that they depend on.
Just looking at all of the companies in this post that are chiming in to say they are helping the tooling, I think there is no lack of effort. I agree that having a big sponsor would help clarify direction.
Worse, too many of the client generation libraries all look to be abandoned. With no real indication for me to know which would have a good future.