"Native speaker" is not a very useful term: it combines a lot of criteria (first acquired language, language you know best, language you identify with, language of your parents, language of your ethnic group etc.), and each of these criteria is further very fuzzy (e.g. I know plant names better in Ukrainian, but programming terms better in Russian, which language I know better? Competency is not a single value, ethnic identification is malleable and people can have several of these, etc.)
These criteria usually coincide in speakers of big languages (usually languages of [former] empires), so it's relatively easy to say who is a native speaker of Russian or English. There are a lot of people who fulfill all the criteria at once.
But they rarely coincide for speakers of smaller languages (usually colonised people). When most people are bilingual, it's often harder to say who is a native speaker of Ukrainian or Belarusian. Most people fulfill some criteria but not all of them.
So, the term "native speaker" is not neutral and not very useful.
I grew up in southern Germany, speaking the local dialect. As a young adult, I thought I could speak accent free German. I couldn't have been more wrong. Many people in Hamburg and Berlin rightfully guessed that I'm from Bavaria. Closely related languages and dialects exist in a continuum ((Max Weinreich: "a language is a dialect with an army an a navy"). Many people in Ukraine spoke and speak "surzhyk", depending on the political climate, they could claim to speak Russian or Ukrainian. Then Russian and Ukrainian, together with Belarusian form a dialect continuum. You can easily understand you neighboring village, but it gets harder and harder, the further you are apart until there's very little mutual intelligibility.
Agree. Especially in Ukraine where the term "native speaker" has been politically charged to an insane level.
I prefer mother tongue.
Oh come on, the term itself is political. It has always been political everywhere: same in Russia and Ukraine.
You can't "politically charge" a term that has always been political. The concept of "native language" is 100% political, always.
As for "mother tongue", it has the same problems and more. "Mother tongue" brings in an implicit idea of 'less prestigious ethnic language', "mother tongue" as opposed to "father tongue" (even in ex-USSR: e.g. you would say that Belarusian is "матчына мова", but you'd never say that Russian is someone's "матчына мова" even when speaking about ethnic Russians — because Russian carries higher prestige, so can't be "mother's" language)
We should not try to replace "native language" with a different term, we should avoid it in serious discussions. Instead, we can speak of proficiency, parents passing language to children, the role of education, the ethnic language, the national language, etc.
And if we do so, we see that there's nothing wrong or unusual about Ukrainian.
If anything, it's huge languages like Russian or English that are unusual. They're different from 99% languages of the world. After all, bilinguals are more common than monolinguals. It's Russian that is a weird outlier, not Ukrainian.