The effect of "meritocracy", at least in this context, is not linear. Every incremental unit of influence or fame (followers, impressions, etc) leads to super-linear influence between some interval (probably tapers off at the tail).
And it is not independent / non-zero sum. If "A" gets more influence, it may take from "B"'s opportunity. And if the growth function is indeed super-linear, then B's opportunity is very quickly squashed.
It shifts the burden away from twitter, thats why it s a smart move. In the grand scheme of things it s not really more meritocratic. A bunch of awareness campaigns will no longer be possible, so we won't know if they had merit