There seem to be 3 general categories of taxes:
1. Incentives 2. Dis-incentives 3. Money to pay for services
Each needs to be examined for potentially unfair rules.
If thinking of an abstract incentive/disincentive structure, you could phrase it as ‘incentivizing those who support me to continue to support me’, and ‘disincentivized those who don’t support me from continuing to not support me’, but those are never the reasons given. To their point, the reasons given can or are often transparently be seen to be the more direct reason, but always have a smokescreen with rational justifications as to why they are not.
If you don’t look at underlying motivations, it’s easy to get caught up in the rational (smokescreen) reasons for something and chase your own tail endlessly without addressing the underlying causes. My 2c
Yes this gets into the meta game of taxes. Aka what actually happens is that the law that gets passed is the one that is the maximum benefit for the party in power that gives the minimum required to get the votes from the minority.
This is mostly true for any legislation though.
Taxes are pretty interesting laws in that they have become this massive catch-all place to push the economy around. It's an endless source of unintended consequences.
A simple system will be inherently unfair.
To get a simple tax system you would need to make everything else simple as well.