A few things I personally find disagreeable with your thoughts on this topic.

Firstly you are assuming the content we are about to get is going to be significantly more difficult, that is wrong, because they have established a relative difficulty for savage and that is barely going to change going into the second tier, just like previous expacs. They mentioned an increase of boss movement or mechanics that make you move, which is nothing new. Almost every second turn going back in the history of this game did the exact same thing and it wasn't a problem. Just look at abyssos our most recent example. Not reason to change in my opinion.

Secondly, the idea that BLM's core identity was the complexity, it is not. It was the engagement felt from a play style that requires timing, planning, practice and knowledge. It changes nothing for people who can't do those things as not being able to plan your instants is still going to be a detriment and if you couldn't do it before you still won't be able to do it. If you can't hit your GCD while doing extended movement you're still going to do bad damage, the only thing lost is the risk factor and by extension the reward. As soon as the people who think they can play new BLM find out their performance is still bad, they will drop it again. And then who would the change be for? I guess we will wait and see for the clear rates in the next savage.