I am just responding to blaming them for not having enough cash on hand to meet the DTC's new deposit requirement, which did come out of the blue. You can say that Robinhood could have anticipated that at some point it may need to back up 100% of the activity of their customers with deposits, given that it is a possibility that is laid out in the DTC rules. But I don't think any brokerage is well-capitalized enough to handle that for every scenario.
But I understand that Robinhood has had other problems (reliability, customer support, etc.), and has also gamified stock trading in a way that is probably harmful. I am sympathetic to those criticisms.