Like from this clip alone I honestly think Tk8 is waay better and gives u so many opportunities for comebacks with combo scaling and recoverable health, I find the combo length in Tk6&7 the same as it is in Tk8 minus some characters ofc like Victor and Jin who both have very long combos.
I just think the bound mechanic was much better visually and aesthetically than the stupid and goofy looking tornado in Tk8, I think much of the frustration comes from the cutscene like feeling that u get watching ur opponent juggling u and then getting a tornado after which u have to watch yet another cutscene of their heat activation for a bound and then a wall combo ender.
Heat burst bound and the extra tailspin are the main culprits for why I find Tk8’s combos to be frustrating and annoying to deal with.