Kucoin is currently on Rank 5 by adjusted volume. Before Kucoin is really on the bottom of the list, but as time goes by, they are climbing.
But if Binance compares to Kucoin, it's still very far for me, especially if we will measure it on the volume, not even 50%.

But there are lot of things that why you should use Kucoin instead of Binance sometimes, especially for me when you are hunting a hidden gem altcoin, because most of listed altcoins in Binance is already pumped or ROI is likely low.

Another thing is why I am still using Binance, is because their P2P. It's really easy to convert your fiat currency to cryptocurrency or vice versa.