I remove 2 of your exchange list on my exchange list.
I was surprised to see those too exchanges listed too. The exchange industry is a very competitive one so once you go off media coverage or stop improving on your product, you become less important and don't make much impact to the success of a project via price gain through volume coming from your exchange and that's exactly what those two exchanges highlighted above are experiencing. Back then they were the best, my very first Centralized exchange was poloniex but the lack of them listing new tokens during the 2016/2017 altcoin gold rush made then lose customers I was one of those as I stopped using the exchange.
Both Polo and Bittrex are in the crypto industry for so long already.
Though some might find them not a good exchange to go to, but for me, I trust these 2 exchanges as compared to new ones.
There was a time also that I stored my btc in Polo, and nothing unusual happened to me.
So I believe people have different perspectives on this matter. As long as it caters to me in what I deemed is right, I think that's one good exchange to go to.