This because Bittrex has the wide are of security for their client from the two-factor authentication to the email verification with IP details.
2FA and email verification only secure your account in Bittrex, what if Bittrex got hacked? Your 2FA and email verification will be useless since the hacker can easily steal your crypto. Also there are so many other exchanges provide 2FA and email verification,
not only Bittrex!
Looks like many above users recommend to use Binance, actually not a "worst" choice since it's popular and trusted, but the problem is
centralized. If you put your crypto in centralized exchange, it's like you trust your crypto to third parties. If the third parties got hacked or become scammer, your crypto will be gone.
I really recommended to use decentralized exchanges or P2P platform (e.g. bisq, airswap, etc)
For those users trust binance since you can trade without need to submit KYC, you may also read
BINANCE - Suspicious exchange behaviour - KYCThey also help people if a hacker sends the fund through their exchange, they act on it accordingly.
This because binance can still recover the loss from the hacker, we can't know the future what will be.