I cannot even take seriously claims how pokemon master title is just some made up childlike desire which "apparently doesnt exist in pokemon world". Making as much sense as "Ash coma theory".
I mean sure its nice to have headcannons and fabricate things to better suit your own theories and formed perception about pokemon anime and how things function there.
But facts and canon are entirely different pair of sleeves.
Maybe pokemon master or type master claims could be brought in question of just being "selfproclaimed titles" or dreaming of something which cannot be achieved if it werent for official tournaments, competitors and tasks established in this series which proved to be steps which push somene closer toward obtain of such title.
With water pokemon master goal and Misty it was stated to mean becoming strongest water trainer in world wanting to become strong as E4 member Lorelei. There were introduced elemental based tournaments like Whirl Cup which test water trainer adaptability and learning how to use water specie to full potential proving worth as type specialist on global basis. With winner accomplishing one of important tasks necessary to come closer toward that title.
Talks from sea priest Maya and professor Elm only reinforced this when talking about water pokemon masters being sea heroes in past who used power of water spirits knowing how to read hearts of water pokemon becoming like one.
With winner getting title Alpha Omega of water pokemon pendant wth mystical water powers.
It wasnt properly explained and there were left unanswered questions. But this moments showed how there exists official steps and requirements needed to be accomplished to gain water master title and recognition of becoming true water expert.
With Iris dragon master was established to be powerful dragon trainer who has immense knowledge about this specie, learned to raise them in most productive way and how to establish two way comunication between dragon and trainer. Becoming perfectly coordinated in battle.
With those who achieved this being assigned this title by elders from dragon village. On top of that Opelucid gym leader Drayden was introduced as dragon master in anime achieving this title from elders at village after passing tests and proving his expertise.
Than there is Ash. His goal of becoming poke masterwas stated several times to become strongest and most recognized pokemon trainer in world. We know how one of steps on that road is to enter gyms, collect badges and win regional league. As well becoming true experts in using your pokemon to full potential and achieve synchronization to work like one if all those high class trainers like champions such as Cynthia, Alder etc are something to go by.
Future steps in Ash career of becoming master were given over course of his journey such as clear confirmation by E4 Lucian on episode "Elite Meet and Greet!" how after regional, there is champion league comprised of battling E4 and champion as one of steps needed to overcome in order to come closer toward pokemon master title.
Accompanied with ex pokemon director Masamitsu Hidaka interview from 2008. on pokebeach how anime will end with Ash becoming pokemon master.
From interview made by mr. Hidaka:
P.S. Last but not least important if pokemon master title is fanciful in pokemon world than whole point of existence behind pokemon league committee and organization which introduced tournaments and tasks through which trainer can make name for themselves, evaluate their skills and acquire master title.
Is brought in question and whta piurpose they serve if anything they promote and established in pokemon world is just "one big lie". To deceive trainer minds in working toward something which was never there to begin with.
Talking about conspiracy theories with people giving too much credit to writers and storyline of this anime. If they think writers would ever go that deep.
Not to mention Nintendo and Gamefreak shoot themselves in leg since day one. Because through pokemon games they established how type pokemon master title exists wizth every E4 member being labelled as type master of pokemon specie they specialize in. Acknowledged for ability to extract full potential of type they train on surface.
How there exists special organizations and clans formed by masters of partioular pokemon specie. Like dragon master clan led by Lance grandfather being mentioned in games etc.
Moral of this story is how just because pokemon master or type pokemon master careers were unpolished and uncleared in some aspects. Not receiving enough exposition. Does not mean how this goals Ash, Misty or Iris pursue are nonexistant.
