>>56195163All of Ash's female companions minus Iris were popular in their times.
Serena especially so because unlike Misty, May and Dawn she had zero personality besides wanting to get in her crush's pants and being a girly girl ... And empty Shonen fanservice girlies like that sell well among the average Shonen fan, coomers, little boys learning about the existence of girls and little girls who still don't know better.
She's the worst companion maybe only after Iris (not counting Gen7+ anime because they changed the formula too much) but it is a well-known fact that most people enjoy eating shit when sold in a nicely decorated package.
