Answering main question as thread is to large to read.
KT is in a good spot, people just don't seem to understand how to use it. as it's really hard to get, and it happens so late that it doesn't see much action.
If you are talking 4v4s, you have to take the entire match into account.how is your enemy playing, how your allies are playing. and so forth.
In 1v1s i feel it's really strong, vunerable with how much of a slug it is, but really strong. and if you lose it you probably did something stupid, you threw it for a win, or you got bad RNG
Other team game formats it sits nice.
I've literally never seen it used properly/well in a 1v1 game across the past thousand games or so. I've never seen it in the hundreds of streams I've watched.
I've seen it being used as a humongous victory cigar on occasion. Virtually all of the games which featured winning + KT would have been won without the KT anyway.
Many Allies players mistakenly think the KT won the game, especially when they struggle to deal with the KT, without looking at the fact that it was already a game they had already lost with 99% certainty.
The OKW player was already winning by a ton if he could hang in there while building all 3 tech buildings and floating a ridiculous 720mp and 280fuel and using up 1/4 of his pop cap. When GenMe can't counter KT + Panther with 1 SU85 and 1 T34-76, the answer isn't "KT OP", or even "KT OK". KT sucks - the Soviet player having less than half the fuel in vehicles is the actual problem.