Introduction

Taxes are typically meant to be proportional to money (or negative externalities, but that's not what I'm focusing on). But one thing money buys you is flexibility, which can be used to avoid taxes. Because of this, taxes aimed at the wealthy tend to end up hitting the well-off-or-rich-but-not-truly-wealthy harder, and tax cuts aimed at the poor end up helping the middle class. Examples (feel free to stop reading these when you get the idea, this is just the analogy section of the essay):

Computer programmers typically have the option to work remotely in a low-tax state; teachers need to be where the classroom is.
Estate taxes tend to hit families with single large assets (like a business) harder than those with diverse investments (who can simply sell assets to pay for taxes), who are hit harder than those with enough wealth to create trust funds.
Executives can choose to receive stock (which is taxed more favorably) instead of cash to the exact percentage they desire. Well paid employees are offered stock, but the amount will not be tailored to their needs. Lower level employees either are not offered this, or are not in a position to take advantage of it.
The legal distinction between a business (whose expenses are tax deductible) and a hobby (deductions not allowed) is based on whether the activity nets you income (there are complications and you can sometimes prove a money loser is a business, but this is a good rule of thumb). Small business owners (e.g. lawyers) can fold their occasionally-revenue-generating hobby (e.g. photography) into their real business, enabling tax deductions for their hobby.
IRAs, 401ks, HSAs, and FSAs all lock your money up for a time or purpose, in exchange for lower or delayed taxes. You can only take advantage of them if you’re sure you won’t need the money for another purpose sooner.
More examples here.

Note that most of these are perfectly legal and the rest are borderline. But we're still not getting the result we want, of taxes being proportional to income.

When we assess moral blame for a situation, we typically want it to be roughly in proportion to much power a person has to change said situation. But just like money can be used to evade taxes, power can be used to avoid blame. This results in a distorted blame-distribution apparatus which assigns the least blame to the person most able to change ...

Moral Mazes