This is something I noticed a while ago and am probably not the only to as well.
It seems like almost every race on Azeroth is not native to it or at least not naturally evolved on it. For example, many of them were spawned from Ancients created by the Titans: Pandaren (and the Furbolgs) came from a bear spirit (like Ursoc), murlocs from a frog, and tauren from a bull spirit. Others were the result of the Curse of Flesh turning Titan constructs into mortal beings: Earthen in dwarves, mechagnomes into gnomes, and keepers into vykrul (which in turn spawned humans). And finally, the orcs and draenei both came from other worlds.
But nothing has really been said about the trolls and goblins. They seem to be actually native to Azeroth, as in they naturally evolved from the wildlife there. One could argue the trolls came from a dinosaur or a lizard spirit (hence the Zandalari’s scales and their regenerative ability), but this is inconclusive. Kaldorei (and the High/Blood elves by extension) did naturally evolve, but it is suggested they evolved from dark trolls who were exposed to the energy of Well of Eternity.
True, goblins got their intelligence from titan experiments on them with kajamite, but other than that, they seemed to be there before the titans arrived.
In conculsion, I just noticed almost race on Azeroth is not natural to it and can pointed out to the Titans somehow, except for the trolls and goblins (And orcs and dranei, but again, they lived on Draenor before they came to Azeroth)