I always thought the same. His KO loses being Garcia: very green Ken just starting his career, early loss Foreman: I mean, regarded one of the hardest hitters and strongest men in sports history, no shame. Shavers: ALSO regarded as one of the hardest hitters in boxing history Cooney: great finisher and finished Norton who was near 40 Norton was out of prime last two as well, but I don't believe it would have gone any different if he fought Shavers and Cooney in his prime.
I haven't seen the Holyfield fight in a while, but with Holmes, Mercer just fought dumb. He let himself be drawn into fighting the fight Holmes wanted to, and then he let Holmes get into his head. After the very first round of the Holmes rope-a-dope variant, Mercer should never have been drawn into that again, and should have walked back to the center of the ring every time Holmes tried it. Then again, I can't really call the guy low boxing IQ with the hell he gave Lewis. So I guess I'll call him inconsistent. I like Norton, but he didn't have the greatest record with big punchers, and Mercer could bang..
Worth noting that he was a relic in the Cooney fight and the same guy blew out both Lyle (1st) and Young (4th RTD.) He was already 36 during his fight with Shavers. Old or at least fading by any standards, especially for his style, and the losses to Holmes and Ali took a toll on him in my opinion. After the Earnie fight his career continued to quietly die. Still, the main reason he lost was pretty much ignoring his corner and trying to inside fight with Shavers (bad idea at this age and with this kind of puncher), probably hoping to break his chin or tire him out. Should he fight smart and box before going to the TKO, I'm pretty sure he would win the fight comfortably. Foreman fight is his only loss to a big banger while in his absolute prime and not a soul in the world should blame him for it. 99% of boxers entering the ring with George that night would get smashed. He was focused, patient, and determined to shut up the critics.