Islam is great, but there would be a lot of asterisks around his title reign if it stopped after Moicano. Only 1 of his defenses was against a top 5 LW (Dustin), and I didn't think he looked particularly impressive in that fight.
In the end, I think Islam will end up with the best LW resume we've seen, but almost everyone will realize he's not the "best" LW we've seen. The best versions of Khabib and BJ were clearly better than Islam, but they didn't have the longevity.
Either way, in a sport this young, GOAT debates are pretty silly. In the next 20 years, the supposed GOAT mantle will be passed around at least 2 or 3 times.