I'd concede that if you are talking about P4P and being well rounded, Johnson is hard to beat. GOAT though? GTFO. Everyone turned their gushing from Rousey to Johnson and although DJ is much more skilled, his division has the same problems.
Someone also made a good point. DJ doesn't have a single win on his record from someone that is a future Hall of Famer or legend. How can you be GOAT if you are fighting nobodies?