Hmm, I was thinking it was dubious how Jack's love interests on Dawson's Creek were so fleeting, but looking through the credits, none of the characters who were primarily there as love interests lasted for multiple episodes in multiple seasons. Jack still has the disadvantage cuz the other main people can all hook up with each other in circles, but still; that's more fair than I thought.
Really, outside of the quintet and family members, it's just Audrey who gets to be featured in multiple seasons and she got upgraded to main cast.
Very different from, say, Buffy where several people would show up across seasons despite the central group being just as close with each other way over anyone else.
Even Pretty Little Liars has a fair number, like Noel Kahn, Jenna, Lucas, etc.
Out of their most remembered hits (this, Say My Name, Survivor, and Bootylicious) IW is definitely the most forgotten. It's like on the same level of memorability as Bills and Jumpin' tbh.