From what I can see, taxation as GDP percentage was never really under 10% since 1950, while big cuts to the top tax rate happened in the 60s and 80s (and the federal budget was continuously in the red since mid 70s basically, with one brief exception before 2000).
> Top marginal tax rate was surprisingly not too correlated to government revenue
Yes. Which is interesting, but also makes sense if you assume that a frequent goal is to shift the tax allocation between wealth classes (adjustments to top rate would be somewhat compensated by other changes).
I think it is always too easy to find arguments for almost any position in data like this, because the overall picture changes dramatically over just a few decades; wealth/income percentiles become qualitatively different as GDP grows ("workers class" pre WW2 is quite different from the same income percentile now) and the data is noisy too, so if you squint you can interpret almost anything in there.
In a perfect world, we would have twenty identical Americas with fixed tax policies, and be able to compare their development over decades; what we have is instead a bunch of different nations radically changing their behavior basically every time a different government comes into power, and many conclusions are inevitably just educated guesswork.
It's a spending problem. You're anchoring on a talking point with out actually running numbers.
Don't believe me, run the numbers yourself.