All trading will cease on Dec 4th.
For old hands, Bittrex used to be the main altcoin exchange along with Poloniex. Back then Coinbase and Kraken only traded bitcoin, so all the alt action was on Bittrex and volume and liquidity were good. It was one of the first exchanges to list Steem when it launched in 2013.
Then they decided they wanted to offer trades against fiat and it all went downhill because that required verification.
Their verification process was more complicated than on other exchanges. At the same time, Coinbase and Kraken started listing alts, so unless you were trading the smaller coins people thought, why bother. Then Binance came along and finished them off.
With fiat trading came scrutiny from the SEC, and this year they got fined $24 million. With their tiny volume, that made them unviable.
If they'd just stuck to being a pure altcoin exchange with no fiat, they'd probably have survived.