There are many other fighting games than Tekken 8. You can even play Tekken 1-7 if you want to. I can understand that people might get upset when developers change mechanics in a live service game, but again, play something else then.
You have to have this notion that if something is called "Tekken" it has to fulfill whatever you have in your head. That is simply not the case. Just because Tekken 7 did everything for you does not mean Tekken 8 will.
I can complain all day that the Battlefield series went downhill after B4, someone else will say it was after BC2. All of us are subjectively right.
It is interesting to discuss how mechanics change and what impact they have on the game. The previous example of 3-second uninterruptible animations are something that takes away agency of the player, but at the same time gives players a pause to think about their strategy etc. You can look at it in many different ways.
You are proving my point. There is no point us having a discussion if you are trying to excuse broken games and cannot accept legitimate observations and complains. You just want people to shut up and you condescend who ever has a voice about it. People aren't complaining about change. They are complaining about broken gameplay and games that are more frustrating than fun
As for what is wrong with Tekken here is an example video of literally broken gameplay
Jack has an armor move that absorbs attacks which then can be followed by these options: a homing attack that controls sidestep, medium frame traps, high frame traps, and a high guard break that guarantees damage that will destroy you if you also happen to be near a wall.
There are so many options fast mix ups in Jacks repertoire during the armor stance that cover so many opponent defense options with very high reward that the skill of execution of high damage from Jack is super low, whilst the defense capability of the opponent requires much higher execution. To evade the guard break, it requires perfect frame sidestep or ducking, but good luck when there are ton of fast mixups including a mid homing. You block a guard break by accident you die. You don't sidestep perfectly you die. You duck and you get jacks new fast mid you die. You sidestep and get Jacks homing you die.
Basically make one or two mistakes and you are done for.
Jacks new combo takes more than half of the bar and once the opponent is on the floor after the attack, he can just spam stomp which stuns the opponent on the ground. No skill whatsoever, not much to defend against, not anything the opponent can do about it. It's broken.
Then Jack can just continue spamming brainless guessing 50/50s. Tekken is mostly a guessing game now.
Something similar also happens with Kuma. He has barely any weaknesses, he had overpowered high damaged attacks and frametraps and ultra high chip damage during heat mode that the opponent is punished for having good defense. His health is reduced to nothing for simply blocking.