Goku is the entire show now so everyone besides him has fallen behind in alot of aspects, previously fully fledged characters in the previous series are now lucky to be even seen at all. In my opinion, it has to be Yajirobe, even in DBZ he never really did anything of importance outside of his moment in the Saiyan saga, at least Yamcha is still remembered regardless of how negative it is, Yajirobe could die off- screen and noone would notice, let alone care lol.