I can't believe I have to clear up what "acting" means, but here goes.
Having not seen the movie yet I can't comment as to the quality of the performances. That said, seriously people, it's called "acting" for a reason. If Bardem was the best actor available to play Desi Arnaz that's all that fucking matters. It's not just that it doesn't matter to me that he wasn't born in Latin America, I'm telling you that if it matters to you that you're a fucking idiot.
This isn't black face.
This is such an odd and extremely recent trend. I remember hoping that the gripes about the lead in Get Out (Daniel Kaluuya) being British would be passing thing; but, it's becoming more common and more aggressively stupid.
Think about the gall of these people who would tell Jordan Peele, a black American making a movie about the experience of a black man in America, that he's missing some substantial moral mark by casting a British dude.
Gus Van Sant made his film Milk in 2008. Gus Van Sant is openly gay and has been so since way before it was cool and Milk is a movie about the struggles of the gay community that he grew up in. All but one of the main characters in the movie are gay but not a single actor in the movie is gay in real life. In 2008, there was no problem. Are we going to call it "progress" that we now suddenly have to cast actors who are real life versions of there characters all the way down to region of birth?
Should a British actor never again be allowed to play Hamlet? Should we now find it offensive that Ben Kingsley was in Schindler's List or Al Pacino was in The Merchant of Venice while not being Jews in real life?
Hell, back when I was acting, I played Jewish characters a few times, I played a woman, hell, I even played a child molester once. It's too bad that that role didn't go to a real pedo, right?
Acting is literally the - ahem - act of pretending that you're someone or something that you're not. Yes, if you actually regard bitching about the next actor to play Romen not being from Verona as some kind of virtue signal, I repeat, you're a fucking moron.