I miss the days of strongly typed schemas. It's much easier to fail gracefully.
Throw your support behind https://json-schema.org it's a great effort.
Or use something sane like protocol buffers
I've used protobufs in the past and I REALLY want to use them now, but the human readable aspect of json has always kept me coming back.
If I want to perform some rough tests of an endpoint during development, all I need to do is compose the json request and fire it off using curl. The response then comes back in a human readable format I can parse straight from the terminal. Boom, simple test conducted in less than 1 minute. I don't even need to think about it.
Compare that to protobufs; I need to create a custom client or unit test that'll compose and fire off the request I want to test, then I need to write a bunch of code that will introspect the contents of the response so I can pick out the details. Huge time loss, concentration ruined since I need to actually think about the process, I'd rather just take the extra latency that using json will incur.
This skips past all of the other advantages json has over binary serialization protocols, like quickly being able to parse requests while debugging issues, infinite client language support, ease of sharing breaking requests to help devs reproduce problems, not needing to add an extra compilation step to my deployments and packages, etc.