Your post is almost word for word what I was going to post, right down to the "I'm no finance guy." But yeah, greater concentration of wealth in the 1% in comparison to everyone else seemingly should result in increased tax share.

Easy enough to understand with simple ratios. If the top 1% holds 50% of the nation's wealth, we would expect they should pay somewhere around 50% of the nation's taxes. If their wealth increases to 60% you would expect the amount of taxes they pay to go up by a relatively equal amount.

Conversely the lower 99% would pay an inverse proportion of taxes. If the wealthy are becoming propositionally more wealthy, the less wealthy should be paying less of the nation's taxes.

Now, that doesn't necessarily mean that someone in the 99% will actually pay less taxes, as their wealth is not increasing at the rate of the 1%. It just means that the wealthy should be paying more as their proportion of the nation's wealth keeps growing.

seems natural that the 1%, being so very much richer, and the rest of us being so very much poorer (in relation!), would bear a higher percentage of the total tax burden.

That's another point that I hadn't considered. The rest of us are just less able to shoulder more of the tax burden and, as a result, the 1% end up doing more. And/or the TCJA lowered the marginal tax rates, which just resulted in a shift of the tax burden, such that everybody was paying less in taxes, but they paid a higher percentage.

Hey! That's a good point! Especially post pandemic, they've made huge gains in wealth.

Also, they should probably be shouldering more because 125,000 Americans who earn more than $400K don't file tax returns.

It's a shitty source from a community with no source standards. So you're bound to find shitty titles like this one.