As always great post... But as you well know neither Robinhood nor Coinbase will be perfect, we need a thriving decentralized exchange, with seemless tranactions, low or no fees, which is safe and secure because we hold our tokens until moment of sale/exchange.
Ps. I had this happen to me, on three separate purchases my bank, or visa, charged me three times each. I called my bank to seek refunds on the 2nd overcharge but not yet on the 3rd. It took 45 mins on the phone so that sucked, but in the end all fees and overages were reimbursed.