Honestly I really like the production on core. Not just referring to this topic here, but I want to say I remember many comments over the years pointing out some negatives about core's production... Honestly I think the album flows and sounds amazing even after all this time of listening to it. It has such energy that kicks in from the first second.
I don't think there is anything wrong with Core's production from a technical standpoint, it's just not consistent with the rest of STP's catalog nor with the "sound" that STP would eventually develop for themselves.
Core's production reeks of the late '80s, early '90s when most major-label rock (hard rock?) records were produced with this overly bright, overly processed, reverb-heavy, larger-than-life sound. It just doesn't sound natural. If you like it, you like it but I don't think there's any denying it dates the album as a product of 1988-1992. (Other offenders from the same time period: Pearl Jam's "Ten," Nirvana's "Nevermind" (to a lesser degree), The Cult's "Sonic Temple," Blue Oyster Cult's "Imaginos," Van Halen's "For Unlawful Carnal Knowledge," Faith No More's "The Real Thing," to name but a few.)