There’s also the fact that Quantico has done well enough in post-live viewership and ratings to compensate for its relatively poor Live+Same day ratings.
Going back as far as Season 1, the show has benefited from Live+7 calculations.
Quantico got rid of the flashbacks that viewers didn’t respond to, sticking with one event and its aftermath rather than jumping around in timelines.
Personally, I’m just glad that we don’t have to wait weeks into hiatus to find out whether or not the show will come back.