I would call the original Game Boy well-designed but put the GBC in the same "Underpowered, but a surprise smash hit capturing that era’s sensibilities" category as the Wii.
With the tech at the time, the Game Boy wasn't going to have a better screen without seriously compromising battery life. Case in point, the Sega Game Gear which was graphically way better than the Game Boy but died fast if you took it off the wall plug.
The GBC didn't have the same excuse; it was so many years newer, and it offered very little over the Game Boy other than a color screen. And its color screen still looked like a joke next to a Game Gear. Given how much newer the GBC was than the GG, I doubt Nintendo couldn't have made a handheld with Game Gear-quality graphics but without the awful battery life.
But it doesn't matter, because the GBC had an awesome games library and people loved it.
With the tech at the time, the Game Boy wasn't going to have a better screen without seriously compromising battery life. Case in point, the Sega Game Gear which was graphically way better than the Game Boy but died fast if you took it off the wall plug.
The GBC didn't have the same excuse; it was so many years newer, and it offered very little over the Game Boy other than a color screen. And its color screen still looked like a joke next to a Game Gear. Given how much newer the GBC was than the GG, I doubt Nintendo couldn't have made a handheld with Game Gear-quality graphics but without the awful battery life.
But it doesn't matter, because the GBC had an awesome games library and people loved it.