I like that they shot for the fences, it just didn't make it that far. They fell back on the old "Indian Medicine Man / Spirit Guide" trope. I don't think we learned which tribe Chakotay was from until much later in the series, probably because no one really thought to define it. As for Robert Beltran, I think he's Mexican with some Native American lineage, but the show made his Native American culture a core aspect of his identity. In essence, they found someone tangentially Native American, and made them the poster child for Native American culture in the show. So, yeah, for me it was two strikes, and the hit only made it to the pitcher's mound. There was no excuse for not finding Native American actors for Native American roles, even back in 1995.