Well . . . yes, but that's not the point of the YA classification. It's to designate stories aimed at teenagers.
You're right, that good YA is equally entertaining to not-young adults as well. It often gets an unfair rap as not-serious fiction or kiddie stuff.
YA, as a genre or classification, is inconsistent with what is "appropriate" for young adults . . . you're also right that some of the stories get pretty racy and/or violent, but avoid graphic depictions of either.
But still, labeling something as YA means you're aiming it at teen readers and you're saying it contains appropriate content for teens.