That might be true, but they are probably the best weapons team defenders and flankers. Soviets wont be able to oorah in and flank without tremendous loss. Now they are suffering a bit with the new Guards, but they still do quite amazing at medium range.
I think the reason people find this unit underwhelming is because they are in between to polar ends players see. They either see long range infantry with lmgs ravage in cover or the opposite, shocks and penals whom destroy at short range.
As it is, they are a challenging but highly rewarding unit whom can be upgraded to deal with tanks.
They are also the best mobile defending unit if you use them with the halftrack (which I've only come a crossed a few 1v1 players who do)
You do highlight a common issue that engagements only really happen any more at either buff sniffing range or max range thanks to there being very few "medium range" only units. No (smart) player will ever sprint into your Pgrens, they will just hang out and range and take them down.
If I was to rework Pgrens instead of reducing the cost, I would increase their long range DPS or give them some armor like shocks so they can close the distance to be effective.
Still doesn't really fix how underwhelming they are with shreks though, 120 munitions for a super easy to one shot squad, I normally only find myself getting shreks when I'm going a fuel to muni conversion doc or Luft supply.