Well in the end most if not every human is superficial to a certain extent. He was crazy in the first place to change himself like that for a crush. The artist never showed his face after loosing weight and before surgery and it's probably an average face which would be okay if he would start over his live and find someone else. I think it would only become really shallow if he was really dumped by uke in the end. So I think it's pretty sweet.
People are attracted to someone's appearance. It's natural. Jaehyun himself is a beautiful person so why being attracted to someone on similar level is shallow? And he loved his voice the most, his voice was always number one reason.
Junseok was really fat, with huge glasses and terrible hairstyle and fashion. Changing it all (except for getting plastic surgery) would be just called managing yourself. Most people do that not even for someone but just for themselves.
On the other side. Do you think Junseok would fall in love in Jaehyun if he was like him in the past? How many times did he say Mr. Jaehyun is beautiful? Looks are just as important as character.

Sigh...but the fact still stands that if junseok didn’t get plastic surgery, the other guy would have never batted an eyelash towards him and it would be even more unlikely for him to fall in love with the original junseok...it makes me sad to think someone should change their whole appearance in order for their crush to finally notice them and like them back...some might think that’s the ultimate show of love but idk to me it’s just looks shallow and not truly meant to be ╥﹏╥ I’m real sad, why the heck do I have to think this way WHY CANT I JUST ENJOY THE FREAKING MANHWA UGH