Poloniex has been running for years so we could say that's a legitimate exchange, I had a Poloniex account as well back in 2017 it was running pretty well that is were I started trading on cryptocurrency until I had some issues with it, that doesnt happen to other exchanges, my account was actually locked with a little funds on it, I didn't open it for a long time but when I get back on it I wasn't able to recover it which doesnt really happened on other exchanges like Binance especially when you take a break on trading usually you could easily recover your funds on it. Plus there are a lot of reported issues out there of freezing accounts, and loss of cryptocurrency in the platform.

At this moment the website is still running and I can see that there are a lot of updates that are going on especially with the UI design of there website, still with my experience of using the website I wouldn't going to recommend you go to this exchange not to mention it was a centralized exchange if you are planning to do trading I would easily recommend going with the trusted one and popular one like Binance, here in my country Bybit was also popular. Dont waste your time trading on this platform because there are already a lot of cases and issues on it so for me that's a red flag.