It provides the Soviet a reliable counter which available in large number to superior German tanks in the mid-war.
That depends on how you define large numbers.
Less than 800 Su 152 have been build. Less than 2000 ISU 152 were build during the war.
These numbers are comparable to the number of Tiger E and B tanks built. Wich is about 1900 combined. Not counting assault guns and tank destroyers using the same chassis.
More than 6500 Panther tanks have been build.
The SU or ISU 152 was never plentyfull. Certainly not available in large enough numbers to counter the heavy armored German tanks.
The SU or ISU 152 also isn't a tank destroyer. Its an assault gun. Its crewed by artillery men and organised like this. The fact that it is usefull as anti tank vehicle especially against heavy armor is pure chance. This capablity wasn't even an afterthought during its design. It has been designed as a replacement for the KV-2.
Its a "pillbox buster". Its job is to give direct fire support to infantry. Knock out fortified position and stongpoints. With limited ability for indirect fire.
Later when it was found out that the vehicle is usefull against armor as well this was a bit more emphasised but it never became its main purpose.
The ISU 152 is a pretty poor TD. Its big, slow, badly armored, lacks good observation and firecontrol and its ROF is very poor.
From a technical point of view the penetration of the ML-20 isn't really impressive. Especially not compared to the size and weight of the gun and ammo. Its only the best the Red Army had at this time. The 8.8 KwK 43 handily outperforms it in any way. The only exeption would be shell weight and HE payload. As a tank destroyer the Su 100 is far more usefull.
The majority of German tank losses on the eastern front were inflicted by field guns. The AT contribution of the self propelled and assault guns was rather small in the grand scheme of things. They made great propaganda tools though. Nowadays a large tank is so much more sexy than an ordinary and common AT gun.