The ultra-rich certainly have tax minimisation schemes in place, but by saying that middle-class bears the brunt of taxation, I suspect you're falling victim to the fallacy that rich people don't think of themselves as rich[1]. In the UK at least, the tax burden is fairly progressive:

https://commonslibrary.parliament.uk/research-briefings/cbp-...

The top 1% of earners pay roughly 30% of all income tax. The top 10% pay roughly 50% of all income tax. Meanwhile, the bottom 50% pay roughly 10% of income tax.

That leaves to 50-90th percentile, who you might call "middle class" (although it's debatable whether someone in the 80-90 range is truly middle class) who pay approximately 30% of all income tax. So the whole middle class only pays as much tax in total as the 90-99 range, although their total of pre-tax income is double.

[1] https://www.businessinsider.com/most-millionaires-dont-think...