That depends on what you want it to be. For a data interchange format, having no comments is arguably a strength. For a config file format, having no comments is a big weakness.
Problems are that some tools will rewrite the file and reorder the "comment" away from what it's meant to comment on. Also might complain the "comment" item isn't expected there. I seem to remember package.json suffering from both of these under the control of npm.
Yeah it's definitely a limited solution, and I prefer that JSON be kept simple that way. Many package.json-adjacent configs like the Babel stuff can be in .js files, giving you comments and everything.
Many people use text format protobufs for config. It vaguely resembles yaml, and the schema is enforced by virtue of requiring a message definition in order to parse it.
