That chart doesn’t tell you much at all. Who cares what the marginal rate is, if you’re allowed huge deductions (as was common back in the 1950’s).
That’s why the marginal rate was higher 40 years ago, but the amount of taxes collected was lower.
The top percent or two are sucking up increasingly large amounts of GDP, and they're not paying taxes appropriate for being at that level.
And capital gains taxes push the high end down even more.