generally allied armor is weaker in terms of raw firepower and/or durability/armor. A tiger fights a T-34/85, or sherman variant, or a KV-1, while an IS-2 would fight a panther or two stugs (both of whom outrange it, mind you), occasionally panzer 4s that it can bully.
Allies have their tank destroyers, who are really good machines, but they do not make the tiger obsolete at all. And the tiger has combat smoke and blitzkrieg, which let it be extremely survivable
Oh yeah there's such an absence of allied TDs 😂 If axis can build a panther to counter an is2 then allies can build a td to counter a tiger.