The quality of a Pokemon generation's designs are inversely proportional to the power of the system the games are released on.
The first 151 were designed for a Gameboy, which had a very small resolution, a palette of four values and no color. Designs had to be simple enough to read clearly on a tiny, green blurry piece of shit screen with no backlight. Pokemon had to be defined largely by their silhouettes and large, easy to read shapes. Patterns were limited to very simple markings. It's just yet another example in a long line stretching back through history of great art being born under adversity.
The same is true of the Gen II games, which is why it's the only subsequent generation that actually feels like a part of Gen I.
Starting with Gen III shit got wacky. Now they had a massive color palette to work with at a much higher resolution, and good design sense started to go out the window. And it's all been downhill since then. Too much freedom has weakened the
