Lately a new "Exchange 2.0" taking over. Bittrex & Polo suffer from many complains, locking accounts and many other issues.
Kucoin & Binance are quite different. they have their own token which give benefits.
Both are going very big in Asia and International.
Check out how Kucoin perform vs other exchanges:
https://www.kucoin.network/Your opinion?
This happens because Bittrex and Poloniex are quite strict regarding their membership and withdrawal of funds because you need to do verification first before you can actually withdraw you're money but you can always deposit with that many users cant access their funds because it is hard to get in touch with the help providers. Meanwhile in Kucoin and Binance you can actually trade and withdraw your coins without any hassle thus many people started to use it than Bittrex & Polo.