It would be more competitive, but Justin would still have lost. He was clearly stumped by Max's footwork and distance management in there. Seemed totally at a loss as he was getting out-volumed and had no answers beyond lunging in while winging big hooks or landing the occasional good calf kick.
You have to really rewrite history and stack the deck to create a situation where Justin would've won, IMO. Like one where he emphasized that stiff jab from the get-go, committed more to the calf kick, and maybe mixed it up a bit more in the clinch/dirty-boxing range rather than constantly trying to land singular kill shots in open space. But at that point it's the epitome of "Whatiffery" and I say that as a dude who picked Gaethje pre-fight. Max was simply the better man in the cage.