New mechanics, when first introduced can be easy and brutal because its something "new" however you cannot constantly have entirely new ideas every fight. Ultraxion, very basic just press the button, once people learnt that, next tier they added in more mechanics to go with it.
I agree there is a line where too much is going on and we're hitting that now but that's when they add in new mechanics to complicate it, initially it will be basic but then they combine it with other mechanics to go with.
Some mechanics this tier aren't fun and I think blizzard is learning what is/isn't - Leishi disappearing was new but just became annoying as shit, Blade lord mechanics weren't fun especially P2. So Blizzard learns and moves forward, you can't expect every single fight to be fantastic with new mechanics because quite frankly a lot of mechanics over 15 tiers have already been done