1. You are dodging my point, JPIV counters every single nondoc USF vehicle. Not only that, but also USF AT gun and bazookas bounce on JPIV's armour.
2. If being a casemate is such a huge issue as you say, I guess soviets shouldn't exist with their stock TDs all being casemates and the other vehicle being Snare34. Puma can take them out if it gets good angle on them. Also JPIV gets higher accuracy + higher rate of fire + higher survivability due to more HP and armour than SU-85 while not needing as much pen due to fighting mostly medium armour vehicles.
You're
missing the point.
Being a casemate means you can be circle-strafed. Something as small as an AEC or Puma can kill an SU-85 or JPIV if they get behind it. This positionally limits casemates
heavily. They've got to stay in range of AT support or have their flanks defended. In essence, they play like anti-tank guns.
This positional restriction offsets their firepower advantage and gives weaker vehicles a way to fight back.
That doesn't make casemates
bad any more than it makes ATGs are bad.
But can you really argue that an ATG with a turret
isn't more powerful than an ATG with a fixed firing arc?