Edit: it’s kinda ironic you think my knowledge of sql server is outdated when you don’t understand the features supported in sql server to begin with.
You are correct that there is no formal SQL type in SQL Server for JSON. And I am sorry for implying otherwise. Type safety requires a constraint on the column intended to hold JSON.
There is no equivalent to Postgres's GIN indices which would allow indexing on an array in the JSON column. Such a requirement would need a normalized table holding the array's values in SQL Server. Whether this is a limitation or a lack of support for JSON, full stop, seems to me a matter open to debate.
I have seen many successful projects (and participated in quite a few of those) that utilize JSON in SQL Server databases. I will amend my former statement, though, because it obviously lacked nuance: SQL Server's JSON functionality has covered all use cases that I have had and personally seen, but my experience is obviously much lesser than some others', so you can take this experience with as much salt as you like (:
It's definitely a shortcoming of MS-SQL, which iirc is being addressed to an extent in the next release.
There are plenty of points where MS-SQL Server is very nice. JSON support is far from one of them. Even if the JSON is still a step above XML support in SQL Server.
I don't know you or your workload, so I can't comment on its suitability for you. I would hazard a guess, though, that your last proper due diligence knowledge is seven years out of date, or more.