One of the more confusing aspects of orcs is the numerous ways they can be referred to. "Goblin" is a synonymous term, as are "urco" and "orch" in their respective eleven dialects. The dwarves use the word "rukhs," while the wild men call them "gorgûns." In the Black Speech they are "uruk-hai," literally "orc-folk." Physically, orcs are described by Tolkien as sallow-skinned, flat-nosed humanoids with slanted/squinty eyes. Their stature varies from a hobbit to a full-grown human, but with short, thick, crooked legs and bent backs. This, combined with descriptions of long arms and large hands give the impression that orcs are vaguely simian looking from a distance. Unlike apes though they fashion their own crude arms/armor and even possess some equally crude healing arts...oh, and they sing. As for languages, orcs speak a kind of cockney English in addition to a smattering of the Black Speech (which isn't actually their native tongue).
A big problem with much of the fantasy literature that came after Lord of the Rings is copycat authors not thinking very deeply about their influences and source material. Monolith's Middle-earth video games are no exception. By attempting to expand on what Tolkien created the pitfalls, plot holes, and problems not only carried over, but in some cases were amplified. Of course, the well-worn fantasy trope of black versus white, light versus dark or unambiguously good versus irredeemably evil, is worth considering as well. Remember that Tolkien saw Middle-earth as a precursor to our actual history, a time of myth and legend. The concept being that divine influence faded over time, followed by magic and finally binary shades morality until things became the world we live in now (with it's various hues of grey); no more good elves, but no more bad orcs either...except that's not how it actually went down. Again, in the Silmarillion, there are instances of elves doing awful things. Some of the lesser entities in the pantheon who had a hand in bringing about Middle-earth were also flawed in the way Greco-Roman or Norse gods are. This serves to only raise further doubts. If the light did bad things, doesn't that mean the dark could have done some good?
Can orcs be redeemed? Probably not, but since nobody has ever tried it's impossible to say one way or the other. Maybe Monolith will explore this matter further in DLC for Shadow of War. Until then though, I don't blame people for casting a critical eye on something that has never really added up.