You are always warned against using custodial service
But we must have to use custodial service for example if we want to use gambling site then we have to use custodial service. If we want to trade then we have to use custodial service. If we want to buy/sell except p2p then we have to use custodial service. That means we have almost no way to avoid custodial service. But we have to use reliable custodial service.