If we look at trading platforms all are not useful some of them are absolutely scam but some are very unique and helpful like binance and kucoin are such a big platform, they are giving a best platform for trading as well many promotions to make some extra money along with trading. We can not trust all trading platform. Some of them is just come to scam all traders money and gone away so be an experienced trader to gain good things from these platforms.
When he says trading platforms, we can assume that he mean there is general. So, the answer would still be useful but if according to you then we need to be specific because not all of them are legit but yeah those scam platforms are not useful but they are only damaging the reputation of cryptocurrencies because when a normal people see the reports about a crypto exchange scamming millions and billions of dollars they will then think negatively and they won't have the motivation to try them. In fact it have happened many times already, I am talking about the hacks but despite of that, the adoption is still going smoothly fortunately.