Disregarding that this is indeed a game, the MG42 had significant weaknesses in areas where the maxim had strengths and vice versa.
While the MG42 had a RoF that was literally stunning, it could not fire continuously. It also required barrel reloads and a large heavy gun. This was further compounded by the need for numerous team members to operate the gun. It was however superb at its job, suppression.
The maxim, while heavy, was able to fire almost constantly as long as ammo was available. It was therefore far more effective as an automatic rifle, able to lay fairly accurate rounds on target for long periods. It was designed to sweep back and forth, effectively forever so it could mow down advancing waves of humans, aka WWI battles. It was generally reliable and easy to make so it was useful.
While these two guns are technically MG's they function in very different roles in the battlefield. The 42 is technologically a jump from the Maxim, but both guns have very potent impact when used correctly. After WWII the introduction of large scale semi automatic and automatic rifles make the maxim redundant.
No hmg can fire constantly due to reloads and barrel overheat even for water cooled weapon.
The fact that HMG42 and its decedents (MG3) are still in use while water cooled hmg are obsolete speaks values for their performance in real life.