There has many way to buy Bitcoin. If you want to buy bitcoin to hold you can use coinbase. It will be very secured for you. And manny exchanger are available to buy and trade Bitcoin. All are not bad exchanger. And no any exchanger will ban suddenly, if creat any problem they will notify us. So i think CEX are trusted. Even if you worried you can use coinbase. It will be most secure there has no doubt. And overall i tell you can choose Binance, Kucoin etc exchanger. This exchangers are very trusted and they providing security for our fund.