poloniex and bittrex are both silent for a long time

What does it mean ? I do not understand your title and its content. Poloniex and Bittrex are old exchanges, and they went through the hype stage. Currently, other exchanges such as Binance, Okex, and Kucoin are the first choices of investors.
maybe he mean these exchanges not hype anymore like 2017 condition which is new coin hoped listed in bittrex or poloniex. and now binance replaced their position . hype in binance was very high and mostly coin traded there able gain profits.