Okay I'll try to be unbiased and ask you some simple questions:
Do you honestly think the M2 .50 cal at 280 MP and 7 pop (plus being locked behind LT tech) is a better MG than a 6 pop HMG42 available immediately at 260 MP?
Do you honestly believe Rear Echeleons at 200 MP are a better engineer unit than Pioneers for the same price already equipped with SMGs and a flamethrower upgrade?
Is USF's mortar better than OSTs for the same price? (Maybe now, finally but for the longest time it wasn't lol).
Whatever you think of Cavalry Riflemen they are not really all THAT good and certainly not borderline game breaking like, JLI which ironically cost the same as Cavalry Riflemen but are way effective.
Riflemen are some of the best standard infantry DPS performers right out of the gate, with some of the best veterancy bonus and great scaling options with the possibility of getting double BARs. This is widely agreed upon by most top level players with 1000s of games to their name.
On top of that they have amazing light and medium vehicles with unparralleled potential for repairing and keeping them in the fight for longer.
I agree that cav riflemen aren't gamebreaking but nobody has claimed that. OP asked for advide on how to deal with them which is completely legitimate.
If you spend a bit more time asking for advice on how to to deal with various opponents rather than complain about fictional balance issues, then perhaps you could also push yourself a notch up the ladder.