I think type specialist works as well as any other goal; as in so long as you actually have them DOING something related to it, it gives them a depth. I think the recurring problem however is many type specialists struggle to do so. Misty, Iris, the SM cast, a bit too often they're reduced to not doing much to enhance their goal but talk about how much they love a particular type.
Misty in particular suffered up until the closing points of the OS since she ended up kinda upstaged by Ash as well. He had two water types and they were both more charismatic and spotlighted than her team for the large part. She had a full team of water types, but not a lot of them had much of a personality or abilities to make them more significant.
Some say Iris did better since she was at least a bit more proactive than Misty and her typing wasn't shared with one of Ash's team. However, most of her team weren't even Dragon types, her most involved battler didn't even have a Dragon type move. The Dragonite arc was a step up, but was quite controversial in how she abruptly got given a pseudo legendary.
The SM cast vary, but they are limited greatly by how stagnant they are. Kiawe is probably the best handled since he has two (technically three) dual Fire types, and despite Ash having a Fire type (a starter at that) they still manage to contend with him in terms of unique abilities and personalities, and also have the series gimmick tied into his typing as well as a few other bits of the region's lore. Giving Kiawe his own occupation alongside that to be safe does help a bit though.
