Everyone who transferred to 2010s Barca/Madrid looked shredded within 6 months.

Why does this necessitate they were doping? They were leading clubs with the best facilities worldwide, pursuing the biggest trophies in football. There's credible reasons fitness improved aside from doping.

Pro athletes are already working their asses off, and Ronaldo was renowned for being a hard worker even in his youth.

Maybe he adopted new training regimes, went on different programmes etc. All the reasons why people that go the gym for years can get a PT that puts them on certain regimes and make drastic, rapid progress. Again, doesn't necessitate doping occurred at all.