The size and spreading of Yama's Shikai is too great for Baraggan to handle. At the same time that Baraggan will rot away Yama in a few seconds, Baraggan will get one-shotted if he took a wave or a pillar from Yama. These are flames powerful enough to vaporize captain-level Sternritters to ashes. And at the same time that Baraggan's Respira can age away dem flames, the power of Yama's fire pillars erupting from the ground will disperse the Respira, which is still a physical, tangible, gas-like substance. Comparing how much of these pillars Yama can make and the amount of Respira Baraggan can make, even if Baraggan surrounds himself with his Respira and a field that slows time around him, there's no way he'd be able to survive a hit from a pillar coming out from below him.
And we could use Yama > Aizen > At least the top 3 Espada logic.
Bankai Yama's stomp over him is obvious at this point.