The 75mm Pak40 is currently the anti tank gun available to all eligible engineers from the Soviet and German factions. At 100 meters, this anti-tank gun boasts up to 148mm of pen.
While not being effective at BR 5, it can absolutely annihilate any BR 1 or 2 tank while also being very effective against infantry. Few low BR tanks have cannons that compare to its performance.
Why use a tank at all when you can simply build an AT gun to easily destroy any tank or shell the point quickly and more effectively?
There are low BR AT guns in the game that can be used:
The 45mm M1937 Soviet AT gun
The 37mm Pak 36
The 5cm Pak 38
Ideally all the AT guns at low BR would be of the same caliber and performance for balance. I don’t know if what I am suggesting is possible given the current matchmaking system, but eventually I think low BR should have AT guns that at least match the capability of low BR tanks.