Bottom graph.

https://taxfoundation.org/top-1-percent-tax-rate/

Top rate went from 50% to 28%, then back up, then down, then up, but percentage of all federal taxes paid has been slowly rising from 26% to 37%.

That graph starts at 1986. The top tax rate was dropped to 30% from 50% in 1986 -- but it was 90% in 1953.

Here is the effective tax rate paid by the top 1% going back to 1915.

It’s higher now despite the rate being lower now (because there were many more ways to avoid tax back then).

https://taxfoundation.org/taxes-on-the-rich-1950s-not-high/

I find their conclusion that taxes "weren't that much higher" not supported by their graph. In 2010 the rate they show was 30% (it is a bit higher now) and in the between 1945 and 1970 it was roughly 45%. Thats 50% higher. That's a lot higher.

given how "spiky" the graph is, your numbers are pretty much cherry-picking:

1945-1970 is ranging from 35% to 45% -- and it definitely won't average to 45%, which it only reaches once

2000-2017(?) is ranging from 30% to 42%

You've basically taken the high point of range 1 and compared it to the low point of range 2 -- and "a bit higher" doesn't really cut it when you're talking about what looks to be about 37% for the latest datapoint... about half the distance between your cherries.

And it's important to remember that changes in the effective rate aren't only due to changes in tax code. During a recession, when equities are doing poorly, you'll see a decrease in capital gains (which are taxed at a lower rate).