Game Freak: Pokemon Sword/Shield emphasize trainers going through their own evolutionary journey
A lot of what Pokemon is involves training and evolution. For Pokemon Sword/Shield, this will relate directly to the player as well.
In an interview with Kotaku, director Shigeru Ohmori mentioned that the Switch entry emphasizes that trainers are going through their own evolutionary journey:
“It’s not just the Pokémon who are getting stronger and growing, it’s also the player alongside the Pokémon. We have a lot of that in these games with the added focus on reaching the top, becoming the strongest and the greatest.”
Ohmori also mentioned in the interview that Caterpie is emblematic of Pokemon, because “in real life you have bugs that will evolve.” Bug type Pokemon can be found early on in the Pokemon titles, so players will connect with the idea that they can evolve. “That kind of teaches the concept of Pokémon: growing and evolving,” he said.
Meanwhile, Game Freak’s Junichi Masuda had this to say about Venusaur:
“What I always come back to, working on the original Red and Green games, is Venusaur. That kind of evolution chain represented what we wanted to do with Pokémon—creating these creatures that look like something you’ve never seen before, but with elements of the things that you have seen. It really captures your interest to see them on the package, for example. I’d see the games in stores, and they’d be red and green, and looking at Venusaur, you just think, ‘What is this? I don’t really know what it is, but it looks kind of familiar.’ Makes you really interested. That really captures the spirit of producing the original Pokémon games.”