Can I run a campaign with the races more or less as they are described in the Player's Handbook?
By which I mean two things. "Is it possible for me?" but also "Is it a good idea?"
Because I have never done this. Even when I was running the (at least initially) core only, fight the crazy wizard in his tower, desert-y campaign, I fiddled with the races. I fiddled with a lot of stuff: it was in the desert, rather than the woodsily pastoral pseudo-European setting that the game kind of expects as default. But the races, I didn't mess with mechanically, but I did make a number of adjustments or total rewrites to the flavor that was in the book.
Honestly, it was kind of confusing. And not entirely necessary.
In a broader sense, I'm wondering if it's possible for me to run a campaign that more or less makes use of the core setting, as presented implicitly in the core rule books. Greyhawk, I guess.
I might, I think, replace the gods with a traditional mythological pantheon (Norse or Greek, most likely) on account of it being more immediately evocative. And maybe even pull some of the cultural trimmings from that mythology.
Leaving that possibility aside, though, I'm thinking, why not try to actually use what's in the book? Run a semi-standard, pseudo-European, elves like trees and dwarves like rocks basic D&D fantasy campaign. Rather than whatever strangitude I normally gravitate towards.
Because this will be for all, or mostly all, new players. And I'm not sure that saying, hey, the book says all this, but ignore it, because that's not how I'm doing it, is exactly the greatest way to get started. Could be confusing.
And what's in the book, it's got to be there for a reason, right? It can't be half bad. There's the sheer novelty of it. Less useless work for me to get stuck with. And it's really not that huge of a restriction to be under, because the information is, after all, awfully skeletal.