Some people tend to evaluate character activity only on number of battles or tournaments he participated in. Or in how many episodes centered around himself or dealing with growth he/she received.
But there is much more to someone rather than just aforementioned things which is i guess one of more unpopular opinions i have about anime. Since i believe moments where characters share role with others in episodes contributing to resolve of plots such as whole Eevee brothers episode helping Mikey to stand up for himself, gym battles in Orange islands where romance subplot was played with her helping Ash to win battle, various episodes where i saw Misty and Brock do research and resolve mystery such as steal of food caused by Teddiursa or Hundoom etc count as well.
Along with bringing humor and lively dynamic on regular basis making many episodes ennobled and more fun to watch.
For back in day standards and formula which was mainly centered on Ash personally in my opinion Misty and Brock had good or decent focus for most part. Especially in Kanto, OI and in second half of Johto.
I guess it could be said how most focus Ash first traveling companions received was in one way or another connected with Ash development as trainer, while getting their moments at times where they were fleshed out more as characters. Granted Misty got more focus than Brock, but still he had many great moments.
Im sure many will disagree but personally i was fine with role this two had in OS for most part, although more attention toward them wouldn't had hurt.