Generally, there are no systems that are 100% bulletproof. This applies to everything. So, the more power you have, the more likely you are to exploit the existing loops.

Who is actually affected? Those less powerful. Progressive tax system hits the middle class (actual middle class, la petite bourgeoisie, not the modern bullshit redefinition of the term) hardest, making it harder for them to make it rich and compete with actual rich people.

As the effect, rich protect inheritance by trusts and avoid taxes by not having income (plenty of tricks available with borrowing), while people like doctors, lawyers, small business owners fund the state and hit hard limits on what can they make.

Don't believe me? Check how much of the tax income comes from top brackets. You may be surprised. Pro tip: system is very skewed to the top.

If the problem is that the system is very skewed to the top, then isn't the solution to be found in addressing that skew? In closing those particular loopholes?

Shouldn't everyone pay their fair share of taxes? Warren Buffett and others seem to think that they should.

You don’t get it. Tax system is already very skewed to the top, as in majority of the income comes from a few.

The problem is that the top paying those taxes are not the rich people.

Exactly. Income taxes hit those with high income like baseball players and doctors and such.

Super-wealthy can take the time to figure out ways to have no income.

And if you do inheritance taxes and similar things, you get more “universities” and other non-profit “finagling”.

IKEA is an example.

If no system is bulletproof then you're not really arguing against progressive tax, the same way "there will always be murderers" is not an argument against policing.