tbf to tolkien, his orcs are very blatantly EuropeanEmpire-coded, sam and tom bombadil are brown skinned, rangers other than aragorn are dark skinned, every evil group other than Sauron/Saruman & loyal minions is said and/or implied to be tricked or forced into the service of sauron with promises that sauron won't keep--they aren't portrayed as evil for this, imperialism is explicitly and literally condemned even if for technological advancement / profit ("were you ten times as wise you would have no right to rule me and mine for your own profit as you desired"), there's (problematic, but super-progressive for the 50s where even many socialists were telling indigenous peoples they should just assimilate into Canada) ideas of landback for groups dispossessed by the "heroic" nations like Rohan and from very early on we have e.g. Gandalf saying we should feel bad for even his slave-soldiers (still have to fight them tho; can't kill imperialism with love sadly)

Orcs and Urukhai are the soldiers of the industrial-evil (Sauron) and industrial-market (Saruman) Empires and are portrayed as ontologically evil because they are loyal and relatively willing soldiers of an empire bent on slavery and/or extermination and gleefully carry out this extermination. Their mannerisms in this ("just following orders" "give me your number and i'll report this") and mode of laying out their camps (grid based, square buildings) also accord more with a modern euro style military than the "ontologically evil savages" most other fantasy portrays them as.

Orcs and Urukhai are not the conscripts such as e.g. goblins who are explicitly described as wanting to desert and flee back to their holes following the breaking of sauron's empire. A lot of text implies that the ontologically evil "races" in lotr are the result of the evil empires corrupting regular peoples who may be good or bad (e.g. Treebeard muses that Saruman might have combined Orc and Men somehow--the chapter before Ugluk says Saruman feeds them human flesh so this seems likely, ents are noted to look similar to trolls, and when trees wake up they can explicitly turn out bad rather than good). So rly imo we should look at Orcs/Urukhai in lotr less as "an independent society" and more as "commissioned officers of the british army", and goblins/trolls more as "conscripted troops in the british army who want to go home but will nonetheless commit attrocities bc of the racist society they've been brought up in"