I know very little about psionics but my time on this site has taught me that it is a contentious thing. Replace the Psi part of Psi Warrior and it would have done better. The mechanics are pretty good in a void but if you don't think they represent psionics well then how well they work won't matter.
That - or the player/DM doesn't like psionics from a flavor/lore perspective.
Mechanically it's a bit like a simpler battlemaster where you don't get to pick the maneuvers. It can be reflavored somewhat - when I played one he was an old warrior-sage who had mastered ancient mystical gith techniques he had mastered from an old tome.