I don't understand what you mean about their charts, my regular broker has no real time charts at all, and the charts they do provide leave a lot to be desired. RH chart's also allows you to jump between day/week/3 month/etc and get a summary of performance within those ranges (which would normally be tabular data). Plus you can mouse hover over the history to get spot pricing on that date.

High information density has a place, but when it directly results on me needing two different screens to get the information I need on one screen then it is a real problem. For example my regular broker's order flow requires me to have two tabs, one to order, and one to show my existing position's cost basis. That's broken.

I think the situation speaks more to just how terrible existing broker's UI/UX is, rather than RH inventing something novel. They just make an interface that was basically solid, which is oddly rare for brokers.

Google's homepage has better stock charts than my regular broker for example (and RH's charts are better than Google's).