Hot take: I found him acting better before the bearded wrecking ball aesthetic. His acting always seemed a bit wooden to me, but after the change he leaned more into it in my opinion. Definitely not saying he is a bad character or actor of course, he is still my second favorite captain after Picard.
I had always assumed that change was part of the character’s arc. At the start he is a by the books commander and by the end he talks with 5 dimensions aliens, believes he is one chosen to guide a planet full of people and is willing to toss out his morals to manipulate other great powers.
In universe, that works. The sad reality is that the goatee-and-shaved-head look (which Avery Brooks sported both in his previous TV roles and in real life) was considered by studio heads at the time to be “too urban” (ie, “too black”). It wasn’t until the show had established its roots that Brooks had enough leverage to change Sisko’s look to what it should have been from the start.
They touch on this in What We Left Behind.
