The KT can't be a "go-to thing in every single game" because of it's very high price and teching requirements. Many games don't even last long enough for the KT to arrive.
What exactly is it that is supposed to make the KT a viable alternative? It's not it's AI because the P4 and Ostwind are better, it's not it's AT because the Jagdtiger and Panther are better, so surley it must be it's status as a generalist but what's the point of an expensive generalist if it doesnt even outperform the medium generalist at AI?
It's AT can't be improved because it's already very good and it's speed keeps it from securing it's own kills especially now that blitz was moved to vet 3 so it needs better AI to be a generalist worth it's cost.
Right now the KT is a slow veterancy sponge that can push away armor but not kill it because speed and only has regular lever AI, it's simply not worth the risk of saving up for it especially since it can be flanked so easily because of it's incredibly slow turret rotation and has extreme difficulty escaping. I appreciate that they lowered Spearhead to Vet 1 because the suppression is great but it either needs betted AI to perform better as a generalist or it needs a bit better turret rotation or speed to keep it from being flanked as easily.
the KTs strength is in its ability to push back infantry while pushing back tanks at the same time.... it might not be viable in 1v1s where mobility is key but it sure is hell viable in teamgames where artillery saturation and AT saturation force lighter tanks to suffer much greater attrition