I've just viewed 'humanoid' as 'sapient, capable of language and complex tool use, and has free will' Two things in that category could be completely unrelated, but still fall under that. Just like how two creatures in the 'beast' category would be completely unrelated to each other.
Yeah. Humanoid as "sapient" (with related implications) is a useful definition.
A human (humanoid) might be closer to a rat (beast) than it is to a lizardfolk (humanoid). While the lizardfolk is closer to an owl (beast) than it is to a human.
And where species come from varies setting to setting. In one setting elves might be created by a god. In another they might have come from the feywild to the mortal realm. In another setting they might have evolved from animals just like humans.
For some reason, 2014 hesitates to go there, but I find the 4e mechanics of "planar origin" (as well as certain creature types) to be useful and flavorful.
Elf (Fey Humanoid)
Tiefling (Fiend Humanoid)
Dragonborn (Dragon Humanoid)
Orc (Giant? Humanoid)
Goliath (Giant Humanoid)
Dwarf (Elemental? Humanoid)
Lizardfolk (Beast Humanoid)
Notice the catlike Tabaxi is actually Celestial Humanoid.
Wilder (Plant Humanoid)
Warforged (Construct Humanoid)
Autognome (Construct Humanoid)
Plasmoid (Ooze Humanoid)
Human (Material Humanoid)
Hin (Material Humanoid, perhaps is Human?)
Altho the Human species evolved from Beast, the designation of Material seems the more salient designation. Elf originates as Celestial, but Fey is the more salient designation.
Mentioning the planar origin (or a certain recognized creature type) helps emphasize how these species have independent origins − thus can be more easily understood to be distinct and unrelated species, even when they all qualify as sapient Humanoids.
The Orc exchanges genes with Human. It is tempting to classify the Orc as a member of the Human species.
D&D 4e derives the Orc from the Giant which itself derives from the elemental Primordial. This ultimately Elemental origin of the Orc kept it feeling Nonhuman. 5e doesnt refer to this 4e lore as far as I know. But D&D 2024 can refer to it, if it helps shore up the concept of the Orc as a separate species with a nonbiological origin, or at least a Nonhuman origin. The Orc would still qualify as a Humanoid, of course, thus require the appropriate cultural sensitivity when characterizing its species.