I feel like I'm going to get snapped but I said I would post the other fish that is used in the Filet-o-fish so...
Alaskan Pollock.
Which does has a very generic taste to me. Not "fishy" like offcuts or something just nothing outstanding.
Also...if Catfish has already been mentioned does that blanket ban other types of catfish (mekong, channel, saltwater, etc.)