I don't think chosing a wrong exchange is that popular of a mistake anymore by any new trader just joining the market. The big exchanges like Binance, Coinbase etc has made themselves so popular that any new traders can't miss their ads when they pick interest in trading. This exchanges are unlikely to scam so that's taken out of the risk too.
The problem I can think many newbies will face is them not knowing what to trade, this exchange are listing new tokens regularly just so they can get some of that heat coming from this trending tokens which usually don't last long but if you get involved with them and not take out your profit on time, you could possibly get dumped on by early investors.