I am displeased, but at same time realistically not much surprised. Original series in general were known as pokemon period where battles, pokemon themselves being fleshed out that much aside from few and progression toward dreams including rivalries wasn't smething where there was payed much attention to.
Pokemon series during Kanto, Orange and Johto were more designed to be about telling adventure full of drama, kinky plots and unexpected surprises where close grpup of friends discover world. There was more emphasis put on development of humans themselves, their fears, dilemmas and their own instincts. And more focused on emotion, depth and concept of exploring new pokemon, mysteries and secrets of world.
Not to mention writers still experimented, tried out different ideas to find working tune for this anime. Along with lacking experience in how pokemon rivalries should be written. Hence explaining why Gary appeared rarely with rivalry while entertaining and driven with passion, lacked proper structure and build up.
Same applies to Ash companions. I too wish Brock and Misty got some rivals. Someone which would drive them forward, increase suspense and provide motivation, anxiety among main characters striving to catch up to them and surpass. Making their traveling toward destination more challenging along with learning from their wins and defeats.
Misty did tested her skills as water trainer against other trainers developing small competitive fire like Marina from Orange Islands,Trinity and Harrison from Whirl Cup,unofficial gym leader Dorian, Andreas from Seaking contest etc. But it was just one time thing unfortunately.
Shame becaue some were excellent rival material, especially water trainer Marina from Orange Islands who adored water pokemon just as much as Misty wanting to become top trainer with them. It definitely had potential.
But in end like i said different standards were followed before so im not so much bothered understanding why it didn't happened. Beside OS functioned great even without rivals with Ash, Misty and Brock being great and impacting on plot. Containing emotion, passion and really great characterization filled with lot of enjoyable adventures and moments. Despite idea of rivalries and strong opposing views not becoming functional back than.
I really feel that there should have been more rivals. If Misty and Brock had rivals, especially during Johto then both wouldn't have become as stale and as boring as they both have gotten back then. I also think that Gary should have appeared alot more and that he should have battled Ash alot more then the only 3 or so times they battled. I would have like to see them both battle as much as Ash and Paul battled in DP.
I constantly hear this, but i dont think Misty or Brock have gotten stale in Johto at all. Which is basically another word for boring.
Brock was still legitimately enjoyable character imo having several memorable episodes and developed more as breeder.
So was Misty brimming with lot of spunk, sarcasm, flirty, curious and passionate nature showing lot of spirit and flare in standing up for weak, battling, various cute pokemon(Chinchau, Teddiursa, Eevee, Quagsire come to mind), her water master dreams. Being involved in many enjoyable episodes, had basically almost whole Whirl Islands dedicated to her, entered various events like Seaking contest, water racem balloon racem, tried to get Totodile , helped Brock many times about his love issues(like with that girl Temaku)strengthening their friendship etc,
I agree how Misty and Brock should have gotten rivals. It would definitely help to keep them more active, bring more conflict which at times lacked in Johto as well more dimension to their stories,
But while neglected at times, i still actually enjoyed in both during Johto series being overall great characters doing much more than people seem to remember.