I've honestly never seen a single Elise so far in the hundreds of games I've played, implying she's probably hard to use and you'll rarely see her outside of ranked. I guess whether or not a champ is widely considered good doesn't determine how often they'll be used, but then there's also the fact she's a bit pricey.
she's not often picked because everyone thinks she blows.
i don't see her in ranked at all.
and you're right, because some of the best champions aren't played at all.
and she's just as pricey as some other parts of the cast.