Sorry, but Wikipedia also doesn't get to decide what words mean, nor you or I, at least not authoritatively.
Linguistically, tax evasion is: evasion of taxes. I can use the words to describe any action taken to evade paying a tax. The words simply do not imply a state of legality.
That there are domains that overload the terms with extended restrictive meaning is by definition arbitrary and has no priority over natural language.
Usually Wikipedia indicates this by explicitly naming the domain, e.g. "In US tax law, tax evasion is ...", but fails to do so here.
According to the oxford dictionary, tax evasion is "the illegal nonpayment or underpayment of tax." Dictionaries don't decide what words ought to mean, they list what people who use the words mean by them. Yes, taken on its own evasion does not require illegal activity (though it does have a much more nefarious connotation than synonyms like avoidance), but when you put the word tax in front of it, that changes the meaning. When the average person talks about tax evasion, they are talking about the crime, and when someone says something is not tax evasion, it is commonly understood to mean it is not an illegal nonpayment or underpayment of taxes. Similarly the word exploitation can mean a lot of things, many of which are not illegal, but when you put the word sexual in front of it then suddenly it refers to a definitely illegal thing.
Sorry, linguists don't get to decide what words mean. Yes, you read that right. Words' meanings transcend any given definition, and all of the linguists in the world working 24/7 are insufficient to describe all of what a word means, in all places, at a given instant in time.
This is why the court "reasonable person" standards: Sometimes definitions aren't enough. You need context.
If an accountant, under oath says you committed "tax evasion" and then later says "Oh I meant the LINGUISTIC meaning of the word, silly you, you thought I meant the TRADE TERM that fits my PROFESSION? How silly of you" that won't fly, probably.
Curiously, the interests which literally bankroll the making of laws and electing of legislators do get to define what words mean.
"U.S. Policies Favor The Wealthy, Interest Groups, Study Shows"
Gilens and Page analyzed 1,779 policy issues from 1981 to 2002 and compared changes to the preferences of median-income Americans, the top-earning 10 percent, and organized interest groups and industries.
"Not only do ordinary citizens not have uniquely substantial power over policy decisions; they have little or no independent influence on policy at all," the researchers write in the article titled, "Testing Theories of American Politics: Elites, Interest Groups, and Average Citizens."
Affluent Americans, however, "have a quite substantial, highly significant, independent impact on policy," Gilens and Page write. Organized interest groups also "have a large, positive, highly significant impact upon public policy."
Alphabet Inc. (Google LLC's parent corporation) spent $27.4 million in contributions and $12.8 million in lobbying (2019) according to OpenSecrets. That's slightly more than I've managed, personally.
Talking about the distinction between tax evasion and tax avoidance was when I really understood the power of controlling language, and why the ruling classes strive for getting their kids educated since the dawn of time.
There are two terms because they are different things: one is illegal and generally involves other illegal things such as fraud, while the other is legal 'gaming the system'. Gaming is not the same as cheating.
Go on, play games with your friends and abuse the tiniest rules and tell them "ah ah, it's not cheating". See how long you last.
Not respecting the spirit of the law is illegal in most of europe, and it's merely a matter of money being thrown around, preventing any legal action. But every time it happens, Google is found guilty. See their latest 5 billion fine, see what happened with Ireland.
It's "legal" because noone can spend the money to investigate them on their crimes.
According to Wikipedia, the term "tax noncompliance" (or "tax avoision"... bleargh) can be used as a general term to refer to both of those things
https://en.wikipedia.org/wiki/Tax_noncompliance