The suppression is heavy if your units are inside its ark and close to the weapon, that's true. You will get instapinned in the first burst, yes. But the maxim's ark is its biggest weakness. Don't let your troops go hand in hand if you notice that the enemy follows a maxim-heavy play. While one squad is pinned, the other one can simply attack the Maxim from the side or behind. A pinned squad will receive less damage a short amount of time after it got pinned, so don't worry about that squad.
Against maxims in buildings, use mortars (mortars are very effective against the whole strategy in commono). A mortar HT is the maxim's biggest nightmare. Mortars are the maxim's hard counters you cannot deny that.
Also a maxim spam lacks capping power.
While your maxims are all at one place, suppressing a part of my army, the rest of my troops will simply cap the map.
I faced a top 100 axis 2vs2 team yesterday. The ostheer player went for double ost mortar and a sniper.
Guess what, it didn't stop me in the slightest.
And ye, as bananenheld says, i will have a maxim for every squad, flanking is impossible making the smaller arc a non-issue.
And there is the lovely fact that if you go for mortars, my maxims will outnumber your inf squads, making winning engagements that much easier.
And a maximspam certainly doesn't lack capping power, unlike say, going for mortars.
There is no hardcounter to maximspam, nor is there any significant weakness in going for it.
I can know, it got me to rank 22 in 1vs1.