Are these recent comments? Because Poloniex was actually not recommended in the past. The exchange was hacked and many lost their coins. However, the Exchange now seems to have new owners and is being run more professionally. At least there haven't been any such negative events recently. I wouldn't call the Exchange aebr a scam. But if there is no reason, e.g. because a certain coin is only listed there, then I would rely on larger exchanges like Binance or Kucoin.