MariaDB Dynamic Columns VS MySQL JSON, which is more relevant?

Question

MySQL

I came across Dynamic Columns in MariDB. Very similar to an early replacement for the JSON type. Syntactically it looks better than the MySql implementation, but judging by the description it is stored in a blob and does not support indexes.
I would like to hear comments about performance and pitfalls, if someone has used this feature. Is it worth trying to use it at all or it will die as a non-relevant feature.