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I actually prefer Lance's setup of "theme" over "literal type".
Like yeah Dragon is a type but it was specifically meant to be endgame and relegated to very powerful Pokémon; when they decided to make it a FRACTION more common Gamefreak got scared and made a whole new type JUST to counter it specifically, and it's still the SECOND best type in the game years later.
But to my original point, having less Pokémon in general results in more creative arrangements; there aren't 6 endgame Dragon types so he uses Charizard, Gyarados and Aerodactyl, all of which are good Pokémon in their own right. Monotype misses the point of theming in favour of "HURR BUT IT LITERALLY SAYS <type>" so you end up with boring teams like pic related. They're not united by anything except what a box in the menu says. Lance's team is united by a PHILOSOPHY.