If you remove free will from orcs
Which is a solution that works, as long as half-orcs aren't a playable thing. If they are, it pretty much guarantees you can't do this.
But I disagree that the only way forward is to continue going this way because I don't see what niche they'd fit.
Why do they
need to fit a niche? This is completely separate from my "why do they need to be monoculture" line of questioning, just to be super ultra explicit about that, because I'm sure someone will try to tie the two together as though they were one position. They aren't.
Why does a race need more than "it's popular" or "as a creator, I like them" to be included as an option?
But as we have moved away from monoculture because depicting a race as a monoculture is racist, we no longer need this many races.
You don't
need anything as an author. "Need" is a completely inappropriate standard of inclusion. If we're going by what we "need," then LITERALLY NOTHING in the books--
not even human beings--is "needed." (Consider the Redwall books, which never see a human character
ever and yet have a massive fan following. Or, if you want a specifically TTRPG example,
Mouse Guard.)
So, why is this minimalism required? A lack of "need" is not
enough. What mandates that we
shouldn't have whatever races seem fun or interesting or popular or profitable or (etc.), other than "we can't include absolutely everything because books don't work that way and resources are finite"?
If the problem with orcs is that they can no longer be depicted as lacking free-will so they can fit the niche of brainless opponent at the appropriate CR (after you are finished dealing with zombies and before moving to gnolls), are evocative of real-life racist tropes, the best solution would be to remove them altogether, as is the case with many of the races in the game.
Why is that best? You seem to be ignoring the very significant possibility that people like these things...
without needing them to be mindless violent hordes. That people may just...
like buff green-skinned people, whether to look upon, or to play as, or both. Consider roegadyn from FFXIV: they're
basically orcs, but emphatically not mindless. They have a cultural history, a reason why they're common in certain areas and rare in others, and they're found all over even though they're not actually native to every part of the planet originally. Most of them are either green-to-grey ("Sea Wolf" clan) or red-to-brown ("Hellsguard" clan); both clans have representation all over the world, in a variety of different cultures, though they can still trace their origins back to certain areas of the planet.