>>30648681He's the first protag of the series, so he gets top billing, and he comes from a time when there was no male or female option, so its easy to make him show up as the canon protag of his gen.
Other protags don't get that, so people are mad.
He in universe, and people that kiss his ass think he's one of the strongest trainers, but they the player have beat em him which means the protag they played as has, so they view him as overrated.
Its that simple.
Really its no different from any other game that gets a different cast in each game letting its first protag get to do things in later games.