After beating the shit out of Till and being a win away from a title shot, it's a little hard to call Brunson a gatekeeper right now, even though it's what he's been for most of his career.
Blaydes is weird. He hasn't really faced a lot of up and comers. He's just had bad luck and some really bad timing with his two most recent losses, but he's always just there on the verge of getting a crack at the belt. I almost wouldn't even call him a gatekeeper at this point. Rozenstruik and Volkov are more gatekeeperish imo.
The true gatekeepers of the UFC right now are Munhoz, Barboza, Hooker, and maybe Smith.