Cromwell is a pointless/useless unit no doubt about that. It does nothing well and has no special abilities.
UKF you'd think should be able build bunkers too. They are definitely out classed by OST. MG42s (probably the most all around OP unit in the game) are highly punishing to UKF as are the cheese Assault Grens.
The MG42 is far from being op, it’s simply the standard HMG that all others are taken from (At least in theory).
MG42: all around very good.
MG34: weaker in every way to compensate for OKW having better infantry.
M2HB .50 cal: more expensive HMG that can damage light vehicles while still being very powerful vs infantry. Only major downside compared to an MG42 is that it’s more expensive.
Vickers HMG: better damage, worse suppression, no anti vehicle ability but can shoot farther when in a garrison. Trades utility against light vehicles for better area denial when combined with a garrison or trench when compared to the MG42.
1910 Maxim HMG: faster set up time and with a more durable 6 man team, the Maxim is meant to trade firepower for mobility and survivability to allow it to be used more aggressively. (Death loop bug kinda destroys this, but that’s not by design. Hence the current Maxim is considered by many to be up and has been changed a lot in an attempt to normalize it.)
1938 DShK HMG: the only doctrinal only HMG is similar to the USF M2HB in its role as an HMG that can also threaten light vehicles, but is locked to only a handful of Soviet doctrines. (Honestly I couldn’t tell you which one is better on paper, but they are pretty comparable in their intended roles.)
Back on topic, the Cromwell does suck though. I’d like to see it’s MGs get a damage boost so it can be more like a T-34/76 in its utility, but without ram and a bit better vs medium tanks.