If the government wants a tax to be paid they need to make it simple and unconditional. If there are loopholes or ways to legally avoid it, they will be discovered and people will take advantage of them.
In a good and just society there is a large overlap between them, and in others there is less overlap.
But it's impossible to build a legal system where there is a 100% overlap, and it would most likely be a broken society in other ways.
I totally agree with your second paragraph, that the government needs to remove loopholes and other ways for people to weasel out of contributing to society. But there will always be some corruption and a lot of money to be earned by only taking from our shared resources and never contributing back.
I strongly disagree with this one. It's not that hard to not define loopholes and exceptions. Really, a simplified tax system without such should be the goal, and then the circles so match.
the people with money prefer being able to employ someone to essentially skip paying altogether.
But if they couldn't - because there are no exceptions and loopholes - society would be better off.
If you want to use a the software analogy it's advocating for using a simple monolith you can maintain with <10 people vs a distributed micro service architecture you're working on with hundreds of devs and has countless non essential features which can break the spirit of the system if used in conjunction.
Drafting a simple tax system is easy. The thing that would be borderline impossible is getting it passed into law because of vested interests