Of course it's possible, but you have to have something truly extraordinary to make up for it (or be a legacy admit, rich parents who donated to the school, etc.). The B will certainly work against you.
> but you have to have something truly extraordinary to make up for it
Flip that, and you’re closer to correct for everyone.
You have to do something truly extraordinary to get in, with the things you listed as being some of the least common types.
Grades just need to be directionally correct rather than perfect.
Also, a side note about legacy admits…
While the admission rate of legacies is about 33% at Harvard (12% at Yale, 30% at Princeton, and 14% at Stanford), that doesn’t mean that being a legacy was the primary reason they got in.
First, 67% of legacies still get denied — that’s quite a bit.
Second, the folks who get into elite schools often know how to raise their kids in a way that increases their chances to get into an elite school. It’s an advantage, but much more often than not, the applicant put in the effort to make themselves a strong applicant.
The legacy “advantage” comes into play almost purely at the margin, when someone is borderline admit/waitlist or waitlist/deny, and the legacy status will push them to the favorable side. You’re not going to see a substantial difference in the folks who were rated comparably.
People seem to want it to be that legacies are freeloading off of their parents and aren’t really qualified admits, and that largely isn’t true. The exceptions are examples like z-list applicants (which you mentioned) or recruited athletes who also happen to be legacies.