OTOH, characters can absolutely have varying levels of "staying power" after releasing. Depending on multiple factors: how much the character's played (online for example), how the character fares competively (to the point people start associating characters with individual players) etc.
Meanwhile,

and

have not only cooled down due to what you mentioned, but also since neither of them are played as much as Rool online nor have they seen attention-grabbing tournament results (Tweek has used both characters to great effect, but has since dropped them).

is the type of character who benefits from having attention-grabbing tournament results - I doubt a lot of online Jokers would pick him up if not for MKLeo and other pros.
.