However, David McCallum is not Russian. He merely played a Russian.
Okay, now you're just shifting the goalposts. Your own words were, "I personally have a hard time believing that a Russian main character
captain will take center stage of any possible new ST TV series any time soon." (Emphasis added.) You yourself were the one who defined the discussion as being about the character, not the actor. That's what I was responding to.
After all, if the conversation had been about actors, I could've pointed out that Leonard Nimoy is of Ukrainian ancestry, William Shatner is of partly Ukrainian ancestry (as well as Austrian, Hungarian, and Polish), and Walter Koenig is genuinely Russian by ancestry (his parents lived in Lithuania but were ethnically Russian). So that's 3/7 of the core cast who have ancestry in that part of the world (plus Majel Barrett, whose birth surname Hudec is of Czech or Slovak origin). So you might have some kind of a point where Russian characters are concerned, but you've got no grounds for claiming that Russian or Slavic actors have been discriminated against in Trek. You're not only shifting the goalposts, you're shifting them onto much less solid ground.
And if there had been a problem with the Illya character with the American public, they may have played on the Ukrainian upbringing part of the storyline.
Oh, come on, now you're just blatantly making up excuses for your pessimism. Not only is that pure speculation -- "if there had been" -- but the kind of intolerant Americans you're thinking about wouldn't have known or cared about the difference between a Russian and a Ukrainian. All Soviets were "Russian" to people like that.