At this moment the maxim is the worst mg in the game, by far IMO and even with 6 men. Fixing this (if possible) wouldn't make the maxim op, it would make it like every other mg in the game. Whats that? Normal.
When retreating, even with 6 men, it still can be wiped, other mgs can survive even with only 2 men.
And about spamming the unit, how many do that? Not many (anymore), spamming maxims is just a thing from the past that is still around because some got used to it (yeah Zarok, I am talking to you

) and are good at it.
MGs Spam (besides maxims from the past) was never a thing (there where/are some rare exceptions of course ) that's why you don't see it now. Why would people start now?