This is because it's natural for people to view different races as coming from different backgrounds, especially in Medieval fantasy. It's more expected to see several mostly homogeneous nations with unique cultures and offerings to bring to the table, and in fantasy, using them to both unite together against a singular evil, and for some, ally with that evil.

This makes for a more interesting story and lore; it gets people thinking: "Whoa cool, another nation with different people, I wonder what they're all about!"

Whereas in this show, and many like it (Wheel of Time), all nations have been forced together to form a single uninteresting soup where few have any cultural significance or quirks whatsoever, so as to avoid offending anyone with stereotypes, which could lead to (GASP!) mild and harmless racial jesting, stupidly redefined as violence against an oppressed minority group by vocal activists who live and breathe dismantling Western/European culture.

Also these people seem to not read much about the works they mess with, there are plenty of non-white factions in lotr that have less set lore about them.

We can easily add in lore friendly blacks and do it in a way that makes less spoken about factions more interesting.

Why do low effort tokenism when you can do something interesting and still diverse?

All it takes is a bit of effort.

Dwarfs... Hobbits... Elves... Humans... Maiar...there's diversity. Only it's on a different axis.