IMO the main disadvantage of Robinhood is not their execution quality (which is relatively low) but complete absence of any helpful tools to make a well-informed decision.

You cannot easily see what options are over or under-priced IV-wise. It also does not notify of any important events that might affect your options positions.

For example, when someone owns a deep ITM call and ex-dividend date is approaching, it might make sense to exercise that call and buy an identical OTM put. But most retail traders are unaware of such technicalities and therefore in the long run sustain losses caused primarily by such basic mistakes..