Psychic actually is a really crappy typing.
>resisted by steel, the most common and arguably best defensive typing in the game, and infeffectual against dark
>weak to pursuit trapping and to sucker punch mindgames, and weak to u-turn which forces switches and gives the opponent free offensive momentum
>only notably strong against fighting types which are a niche typing and poison which is one of the least common types found in high level play
>only notably resists fighting which is again a niche typing and it resists itself I guess
Psychic types are strong despite their psychic typing, never because of it. All Psychic really has going for it is access to Stab Psyshock in order to beat certain special walls, and common access to coverage moves like Shadow Ball and Focus Blast.