The question is, why do we need a Sherman 76mm? Moreover, it is a doctrine. Does it have more armor and health compared to a standard Sherman? - not. The difference in gun penetration is very slight. Why do I need it if I can take Jackson?
The 76mm is a 75mm that swaps the 75mm's incredible HE rounds for HVAP rounds. HVAP rounds have a penetration of 220/180/165, which is on par with a Jagdpanzer IV. A pair of 76mms can take down a Panther, a boast the 75mm can't make.
The 76mm is a good tank, and definitely worth picking up with you're playing Soviet Lend Lease.
But if you're playing Mechanized? Not so much.
As a generalist, it faces stiff competition from the Dozer upgrade (which gives the Sherman 75 the durability stats of an Easy Eight) and as dedicated AT it's outclassed by the Jackson.
I think you'd see more of it if you moved the Bulldozer upgrade to another commander. Reserve Armour has a weird antisynergy with itself.