When you see current companions having one or two pokemon at best in their entire team than its obvious how writers standards got lowered when it comes for Ash traveling companions. And watching Sun and MOon series I feel Lana, Mallow, Lillie, even Kiawe deserves better, because lack of captures hampers on their potential and ability to develop when it comes to their trainer growth.Whole trend of reducing Ash friends pokemon team size to significantly small numbers started with BW , jut to see XYZ in Serena case and afterwards now SM taking whole new step in not giving them more than one pokemon to work with.
Some will say its quality over quantity that matters. But that don't holds truth in case of their battling abilities and proactive usefulness when having to battle villains, other trainers, wild pokemon and enter rescue missions. Hurting ALOT their chances to join Ash in saving day, get more growth themselves and send message to viewers of being more than just cheerleading support.
Thasts not to say their pokemon of what they have don't have any impressive feats, but sheer fact of having underdeveloped pokemon teams actually do hurts their possibilities of being more active in longer run.
May and Dawn didn't suffered from this issue because they had well established respectable number of pokemon in their arsenal adding to entertainment value and their validity as pokemon battlers/coordinators.
This applies as well to Brock and especially Misty.
People can dump on her pokemon team all they want. But having more pokemon was beneficial in lot of other areas often overlooked. It gave in Misty case bigger variety to her team, more muscle to her trainer career, supported her credibility as pokemon battler. And allowed for rather proactive role in often being able to take initiative and join others in battling criminals or saving others. Even when episodes weren't about her. Adding another reason for people to find appeal in character and got invested into her.
Now don't get me wrong, i wasn't satisfied with how many of them were handled. But i still recognized in them potential and entertainment value. Appreciating Ash earlier traveling companions having bigger pokemon teams.
Because more pokemon someone has bigger chances there are to see human character be more active, get more development from interacting with their teram. And helping them in reaching their dreams easier. With each and every one of them carrying potential to blossom eventually. And this still is valid in these companions less developed members of their team.
Yeah nearly all her Pokemon were utterly stagnant or only got development AFTER her series run was over (five seasons of Togepi and Psyduck being one note comic relief and then they get more justice in one return episode).
Not all though. Psyduck was among Misty most exposed pokemon adding to lot of humorous moments and over course of series it played important role in Misty development on field of starting to get over her initial feelings growing to appreciate what she has. Staryu was one of Misty best and strongest pokemon entering many battles and being her go to pokemon.
Some will say it had no character but to be fair with lack of anthropomorphic features due to design represented huge challenge to animate its emotions. In general every pokemon we can objectively assume has personality and feelings, I mean Misty herself on multiple occasions said how she knows how Staryu feels with certain moments like battle for Totodile displaying strong bond existing between such pokemon and its trainer. BUt some its more challenging to express that than others and that is understandable.
Corsola came later but its feats in Whirl Islands and afterwards defeating several strong pokemon like Espeon, Mantine in Coastline gym, Delcaty, etc and being rather very vivid was example of decently handled pokemon given its short run. Politoad was probably most developed pokemon in character sense, while Gyarados don't need explanation becoming her powerhouse.
Starmie and Horsea sadly were left at Cerulean too early in series never living up to their potential and Goldeen along with Togepi were obviously mishandled. In retrospective Goldeen being aquatic specie was not even problem, Orange Islands were heavily water based, so were Whirl islands and Johto was filled with lakes, rivers etc. So logistically this pokemon could have been used a lot more often but I guess writers preferred to rather stick to amphibious types instead.
Luvdisc and Azurill appeared only in one or two episodes respectively not having enough time to be developed and utilized in more significant manner. But ill say this Luvdisc due to fact of defeating Mightiena and Sableye from Butch and Cassidy proved one thing, it can battle and in fairly effective manner. Unlike its case in games with anime displaying that specie in better light.
In nutshell Misty pokemon team had quite a few gems but since many feats occurred in Johto saga(some afterwards but people don't take that in account despite being unfair and incomplete analysis than) its often overlooked due to bad reputation of series among fans as whole.