Idk what even quantifies a goat. People seem to think it just means a duelist. I think we should be categorizing goats by the roles defined within Agent Select: Senti, Duelist, Controller, Initiator.
Ex., for the GOAT Controller, you could argue MaKo pretty well, for Initiator you could argue Leo.
But for best "VALORANT player of all time" you would be looking at someone who plays all roles well. I would say that quality could be attributed to flex players. For example, if f0rsakeN continues to put up decent numbers in his maximized flex role on PRX, he could arguably be the "best VALORANT player of all time" simply because he's able to maintain performance across a wide variety of agents within all classes.
TL;DR: Can't say one person is the goat of valorant, but you can say someone is the Goat Duelist or Goat Initiator
edit: You could even think about subcategories like best Flash Init, best Scan Init, best Wall Controller, etc, but there are a limited number of agents at the moment and I can see that happening when we get to a League-like number of agents