There is no excuse to suddnly implement KYC without prior notice and freeze funds. The funds, they holded, are the user's funds, so I can't name bittrex as reliable exchanger. as long as users can't withdraw their money, independent from KYC proceedings. Poloniex implemented KYC in a legal and correct way. They gave a notice months before and gave users the choice to withdraw their funds and/or agree with the new regulations.
So, Bittrex will loose its popularity.