All things considered, Mero did fine. Not everybody was meant to be a main eventer and not everybody is supposed to have a 20 year career.
Mero came to the WWF just as they were losing Hall and Nash and Mero was pretty much built up to try and take the Ramon slot of constant IC challenger who can mix it up with the main eventers. The lack of talent around didn't really help, as feuding with HHH was not going to work out for Mero based on the Kliq ties. Winning the IC belt and giving a heartfelt speech on RAW wound up being his face high point instead of his kick off to the next level.
Even before the knee injury he was dicking around on PPV with Leif Cassidy and in limbo as Mick Foley didn't want to work a Mania program with him.