The question is, why are the orcs your PCs encounter generally evil? Could it be because the book says that orcs are evil and you've decided that there's plenty of good orcs, but they're all off-screen where nobody will ever see them? If so, how is that any different than saying that all orcs are evil?
I just decided for my current campaign that orcs exist if anyone wants to play as one (or a half-orc), but since they've been such a lightning rod of negative publicity all the orcs are permanently offscreen because I have no use for them in any capacity.
Since I'm running an Underdark campaign, though, I've featured multiple drow. The most prominent one is a Chaotic Evil magic shop owner who plays nice in the central hub of the campaign but has a lot of shady connections and two bodyguards that are possessed by demons under his thrall. There's also a Lawful Neutral priestess of Erathis, a Neutral (with Evil tendencies) priestess of the Raven Queen, and a Chaotic Neutral (with Evil tendencies) scion of a noble house. All are from a city that was destroyed by a rogue Demonweb spider, and all but the last one despise Lolth for different reasons. However, they all came from a Lolthite civilization, which has affected their view of the world even if they hate Lolth (kind of like how atheists or agnostics from Christian backgrounds can retain certain Christian ideas despite not following the religion themselves).
I've also got duergar in the setting that are mostly Evil, but the dwarves in the area are mostly Evil themselves so there's functionally little difference between them other than abilities and allegiances to opposing homelands. The duergar keep slaves and the dwarves use prisoners shuttled down to the Underdark for labor. The dwarves ostensibly follow Moradin, but for most it's a faith unaccompanied by good works, while the duergar are more pious towards their god Laduguer.
The nearby deep gnomes are Neutral, but have been so traumatized from multiple betrayals both within and without in the last few decades that they've become paranoid isolationists who have adopted a more aggressive stance against anyone who even gets within several miles of their home, teaming up with myconids to use the slain as spore servant guards for the joint myconid/deep gnome colony. The individual deep gnome families barely trust each other at this point and mostly keep to themselves.
Basically, most of the NPCs are some flavor of Neutral or Evil. The few actually Good ones are either powerless or pawns of the more powerful Evil characters.
