the biggest issue with postgres search is the inability to use TF-IDF or BM25 (the current default and state of the art on elasticsearch). The current ranking system is not very relevant.

Anyone who is familiar with PG internals - is there something in the internal data structure that prevents a BM25 or TF-IDF style rank generation ?

The work on RUM seems to have stagnated (and TF-IDF was a todo anyhow here) https://github.com/postgrespro/rum

I have a theory that if they incorporate these algorithms, it makes postgres potent enough that a lot of people may choose not to use elasticsearch/lucene.