Strange how more people think the IS-2 is fine, yet that KT needs buffs.
Because the IS2 is cheaper, faster, has better turret traverse, and is a tech-free call-in vs KT being the most expensive tech cost in the game.
Once you get more experienced with the game, you'll realise that timing is super important.
The Luchs had a 90 seconds build time in the previous patch, making it a seldom-used pick because it came out at the same time as the T70, later than the AEC, and for such a unit, losing a full minute of shock value meant it had a very small window of opportunity remaining.
One of the biggest appeals of Falls (apart from cloak) is that they come very, very early for an elite infantry unit. Obers come at the 10 min mark if you didn't go for a Light Vehicle, and realistically come at about 12 or 13 mins for most games. Falls come at the 6 to 7 min mark, which gives them so much time to dominate infantry engagements and affect the rest of the game's development compared to Obers.
Tech-cost/timing relate to shock value - the IS2 can and often does come at the timing of Axis having just 1 medium tank and saving fuel for another. The KT comes at the time when the Allied player should have multiple mediums AND a 60 range TD. In raw stats alone, the KT isn't much different from the IS2. Timing-wise, the IS2 actually has a window of opportunity and a chance to vet up as well as impose its will on the battlefield but the KT doesn't.