He doesn't hate the album because of the music though, lol.
His personal life was falling apart when he made this and he was doing wild drugs, so he said the album triggers the trauma from that time. He also said most people tell him this is his best joint. But for him personally it reminds him of a low point in his life. Most artists make their best sh*t when they're heavy on drugs and going through sh*t. This is Reggie's version of Mary's My Life.
Or
Pac - Me Against the World
Ghostface - Ironman
Bizzy Bone - Heavenz Movie
Bruce Springsteen - Born to Run
George Lucas - Star Wars (OG) and Empire Strikes Back
Mick Jagger - Aftermath
Etc
We look at and love the finished products, they look at it and see ruined relationships, financial stress and mental strain (incl drug/alcohol abuse).
In Red's case:
Dealing with the loss of Rockafella
Heavily overworked due to his touring schedule
Used drugs as a coping method (he doesn't remember recording the album)
There was a VIBE article yeeaaars ago where he talks to a journalist who told him that during this time Red spent like an hour talking to him about why committing suicide is the only sensible thing to do.
Just stay funky like that / my style like, shhh, a junkie on crack