Yes but at least the 80s heavyweights had one or two very good wins on their records and got a title belt before they either stopped training properly or started doing drugs.
Yeah, knocking out Masaev and beating Larry Donald isn't comparable to the best wins on the resumes of any of the 80's heavies.
Johnson was a pretty good gym fighter. He did in fact get the better of fighters like Ibeabuchi regularly in sparring. But a pro fight is just incredibly different. The smaller gloves, the lack of headgear, the rough stuff, the variables inserted, all of it. Johnson couldn't handle those in the ring, and he couldn't put in the work to avoid em outside. Kiitschko beat the hell out of him. The weight made it look bad, but that outcome was inevitable. Being light helps with stamina, sharpness, chin, long-term things. Getting hit by every single right hand your opponent throws doesn't change cause you drop 20 pounds. Johnson would never have gotten past Vitali.
I was never all that impressed to be honest. Sure, he could have stayed in shape and made more money. he could ahve given himself a better chance vs. Klitschko... at least went out swinging.