I agree.
To look at just one aspect of the discussion, motorsport history is littered with stories of top-line competitors who struggle to adapt to (sometimes minor) technical alterations to their chosen category - look at how Hayden went from World Champ to also-ran when the 800s turned up for a recent example...
I often wonder how the top riders of each era, at their prime, would go if you made them swap bikes. Would Reed/Stewart/Carmichael on (say) an RH72 seriously challenge deCoster, Robert, Hallman etc? What about the other way 'round?
So while it's good backyard barby/round the campfire/forum talk, anybody who thinks they can arrive at a technically indisputable conclusion about the GOAT, is dreamin'.
(None of this is meant to take away from RC's record that earned him the title of GOAT).