Some of the big sellers have moved to their own platform. And, still use E-Bay a bit for the hard to move items, but sell anything easy to move on their own private platform.
For new items, I'll check E-Bay, Amazon, and perhaps a general web search, and choose whatever seems best. It is quite possible that the E-Bay fees are cutting into the bottom line sales prices some vendors are charging. I'm finding quite a few items that are significantly higher on E-Bay than elsewhere.
Still, for used rare items, E-Bay is still king.
I really wish that Yahoo auctions hadn't shut down.
A little competition is good.