It's been considered to be within the same bermuda triangle of scientific vaporware that demarked by quantum computers performing useful tasks, fusion power generation, that sort of thing. Always just around the corner. It's basically a meme in physics.

Room temperature superconductivity is not demonstrably impossible like a perpetual motion machine, but mainstream press picking up on yet another set of amazing claims in this field tends to (deservedly) lead to a lot of eye rolling.

The consequence is that if you've actually made actual progress in the field, you'd better be very sure you are right and able to back it up.