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.
One who exploits a bug is a hacker. An example of a life-hack is to arrange things to have lower taxation than those who wrote the laws were expecting.
But just as bugs in software are not meant to be exploited even though they can be, there are many loopholes in laws that are not meant to be exploited even though they can be.
Unless the law has a generic catch-all for tax minimisation schemes*, such minimisation may be legal, and yet frowned upon because it wasn't meant to be legal. Or even if it was meant to be legal, but you're rich and the general public thinks you're being unreasonable.
* I think the UK does? Or at least that's what it looked like HMRC was saying last time I was able to file my own taxes there…
You can tell the ones which aren't by watching them getting removed in a hurry when the government finally notices too many people using them. 10-15 years back, some colleagues had made businesses for themselves just so they could receive their real jobs' income at the lower rate of dividend income rather than the income tax rate. I am told this is no longer possible.
Conversely there is (or was) what I think was a deliberate loophole for UK inheritance tax — if I remember right (not a lawyer) it works like this: physical objects in your home are all bundled together and valued at £1 for inheritance tax purposes, so fancy art, stamp collections, etc. don't get taxed.