The blog post explicitly mentions the Richardson Maturity model. He also says that even systems or designs are consciously trying to acheive Level 3 in the Ric

The blog post explicitly mentions the Richardson Maturity model. He also says that even systems or designs are consciously trying to acheive Level 3 in the Richardson model (HATEOAS) such as JSON-LD with Hydra or JSON:API are still not RESTful in practice. This seems to be the main point of the article, but it is quite hidden. The idea of an app that can display and manipulate data on a distributed network of servers using a well-defined set of JSON-based content types is very interesting. But this is not what the vast majority of currently existing "REST APIs" (even those who are using a more hypermedia-oriented format like JSON:API or JSON-LD) are trying to do. I personally think it is too late to rebrand "REST". Like a lot of confusing names (NoSQL, Serverless, "Cloud", "JavaScript"), it is here to stay. But the main point the author is trying to make is that there are true Hypermedia API clients (which are virtually non-existent in the wild) and HTTP API with various concepts borrowed from the REST model (but are not fully RESTful themselves).