ABSTRACT. Future users of large data banks must be protected from having to know how the data is organized in the machine (the internal representation). It provides a means of describing data with its natural structure only—that is, without superimposing any additional structure for machine representation purposes. Accordingly, it provides a basis for a high level data language which will yield maximal independence between programs on the one hand and machine representation and organization of data on the other.
E.F. Codd. 1970. A relational model of data for large shared data banks. Commun. ACM 13, 6 (June 1970), 377-387.
You propose to reintroduce a problem that they absolutely wanted to get rid off 40 years ago. Just imagine that you first have to figure out how to painstakingly parse serialized Python dictionaries before you can access the data in another program written in e.g. Rust.
It clearly amounts to UNSOLVING a problem that is now SOLVED ALREADY.