Every single medium tank destroyer in the game is strong against all types of tanks except for ele and jt. How is this unique to the jackson ?
the jackson has the tools that make it far less vulnerable and lacks a weakness thats prone to exploitation its never on the back foot if you are paying attention. an su85 CAN be circle strafed if rushed or caught out of position and its high pen and average rof leave it wanting as a mediumkiller, the su76 while very much over performing in its own right is very squishy and again lacks a turret (although its a zippy little bastard) and deals sub standard damage per shot making it ineffective witout a spam of them against high health pool enemies, the jp4 has the same problem as the su85, the firefly is very slow and its turret, is also slow leaving it vulnerable to flanks/ rushes, without tulips its a very underwhelming beast clearly designed around facing off heavy targets (again the tulips throw a wrench in that becasue of their alpha strike but the unit itself is soundly a big cat killer). and stug has a range of 50 meaning its always ever so close to return fire and again it can be flanked. the m10 iirc only has a range of 50, so a jackson but without sniper ranges and again iirc its slightly squishier making it riskier. the jackson CAN act as a TD with all the drawbacks of others but it can also chase or flee, with great accuracy and a hard hitting gun, its turrets allow its gun to not be hindered by pathing on the hunt or retreat, it can effectively engage mediums or it can pop HVAP and effectively engage heavier armour with more bang for its buck. its got it all and thats a bad design.
it shares the drawbacks of vulnerability to non armour as all TDs do, but thats the end of the list of its drawbacks/vulnerabilities, all others have at least 1 or more checks to keep them balanced (or relatively anyways)