For me, the mark of a great dancer isn't actually the number of flourishes they pull out or whether they're on time for every single figure (although I do think it's important that people at least make a valiant attempt on the latter); for me it's how they react when things go awry, and how well they are able to fix mistakes with as little disruption to the dance as possible.
Sometimes this means finding a way to tell new dancers "go swing over there" if they're completely flummoxed by a hey. Sometimes it's using nonverbal communication to tell your partner where they need to be or remind them of a move that's no longer being called but does come next (e.g., motioning them over if they're supposed to chain to you). Sometimes it's doing a switch flourish to put you and your partner back into the spots for the roles you're intending on dancing. And sometimes it means drawing on another form of dance to get yourselves where you need to be in an interesting way.
Incidentally, this is why I find intentional, good chaos/shenanigans/whatever sets to be fun and valuable things when they crop up. By intentionally subverting the expectation that you'll keep your neighbor/shadow/partner, you can see how to fix it if you've accidentally lost them, while still keeping the flow of the dance, instead of generating a train wreck.
Being able to think on your feet and improvise also can help recover you when you've completely and utterly botched a flourish. (It happens; you put your wrong hand on top, you turn your partner under the wrong side, you realize halfway through a swing that you accidentally traveled and continuing the swing will slam your partner smack into someone else who traveled...). And if you improvise your way out of a flub really well, you can come up with a variant on the flourish you were trying to do...and, uh, you meant to do that.
What are some of your favorite improvised moments on the dance floor?