There is no such thing as the GOAT. People should just stop with that shit. There are those who were the best in the era they played in and that's it.
Without modern medicine and technology Messi wouldn't be able to play in the past and even if somehow he was treated back then I find it hard to believe he would do well with how physical the game used to be.
He would be carried out with a broken leg on a match like that one in 74' against the Netherlands. Or that Brazil - Netherlands that same WC. Players of today would cry for their moms after the first kick to their knee.