Djokovic clearly obtained his success through performance-enhancing drugs. Not the GOAT.
Djokovic explained his initial burst of dominance as being a consequence of going "gluten free". Murray was asked around that time if he had tried it, and said he was weaker when gluten-free. Djokovic later started eating gluten again but his dominance continued... thanks to PEDs.
His fortunes took a suspicious downturn at the precise moment of the well-publicised Sharapova drug bust. OFF the PEDs... for a while, anyway.
Djokovic threatened to sue a journalist who once wrote that he was serving a silent drug ban. He then backed off and took no legal action... because he was on PEDs.
Murray publicly advanced the idea of more frequent drug testing. Djokovic and coach Boris Becker spoke against it.
Djokovic is on a years-long warpath against COVID vaccination. Not for honourable reasons, but because of the possible interactions with his PEDs (which have also freaked numerous gassed weightlifters and sportsmen).
Then there's his penchant for mysterious, extended toilet breaks in which he takes his bags along with him. His bizarre ability to play extended five-set games into his late 30s, while showing zero fatigue and very little sweating. His trademark eye-popping rage outbursts on court. His liking for suspiciously inhaling from "water" bottles while seated at courtside.
Djokovic owes his career to PEDs.