>>55110652steel gained even more relevance as a check to fairy so steel types became more popular, this also fucked over psychic pokemon
dark type was buffed to absolute insane levels with knock off, dark itself is also just a very strong type with plenty of strong pokemon and knock off if literally everywhere, so even if you arent staring down a dark pokemon, youre still gonna get smacked with an SE move
psychic terrain didnt really do enough to buff the type the same way grassy terrain did
fairy type fills psychic's niche of beating up fighting pokemon, fairy also has the added advantage of beating up dark pokemon. Psychic being SE on poison is barely worth anything these days and it has virtually no defensive utility thanks to only resisting fighting, which fairy also does, and itself
ghosts are everywhere and also stupid strong
tl;dr fairy makes it near irrelevant by gobbling up its niches, the type made to check it, steel, is sitting top tog because of fairy, and the type made to outright counter it, dark, is right behind steel as one of the best types to have offensively. psychic is holding on because of all the powerful legacy pokemon that were made psychic but i think literally all of them would enjoy being fairy more.
if they wanna buff psychic they either need to give it a new resist or keep giving it fucked up gimmick moves like psyshock