That is not true. Most heavies regularly bounce panther's shots. Unlike axis heavies which almost never bounce jackson's, Fureflie's or SU85's shots.
I'll assume you've never built KT. Unvetted TDs will also bounce off of regular tiger, take into account their lower, far penetration instead of high close penetration, because you'll almost always use them from afar - unlike panther.
On top of that all the above are 60 range and are much cheaper (panther is 50 range and much more expensive). They also have abilities that help them even further like focus sight from su85, tulips on firefly, and self repairs plus extra shot on Jackson and better moving accuracy. They also get much better AT abilities with vet. Panther basically can be kited by them and must rush forwards exposing itself to AT fire. They can stay out of range.
They all also have half the armor panther got and much less health. Panther got off guard can run away, allied TDs not really. Panther also got abilities to help it either chase or run away, both stock and doctrinal. OKW Panther with elite armor commander can deal massive damage with pretty much guaranteed penetration on anything lower then IS-2, ost Panther can chase/run away for much longer and has access to best tank smoke in game thorough meta doctrines.
Panthers are also useful vs infantry, while allied TDs can do absolutely nothing here.
What about isu152
Can be taken up frontally by panther.
kv series (especially with hull down)
Helpless, outranged.
or is2?
Outranged until vet2, if its vet2, you should have more then adequate AT on field to force it off, if you don't, you lose game way before that.
Different types of Churchill's, etc.
Outranged and not meant to be fended off by single panther altho it will do the job.
You need volume of fire against them, not reliable penetration.
Some of them are very good at both at and ai.
That's IS-2 exclusively.
You could argue ISU, but no one gets ISU for its AP shots.
Not true. The only stock axis unit that is even here is jagdanzer with 60range. The rest will be outranged by tank destroyers that can sit relatively safely behind lines and deal damage.
Tank destroyers are not meant to fight tank destroyers, however JP4 just so happens to be a hard counter to all allied TDs. Also, again, why don't you have any ATGs? They have the same range as TDs and keep TDs away, use them. If that's too hard, both axis factions have "you can now no longer use vehicle based AT" buttons in form of ELE and JT.