It took Game Freak six years to develop the first Pokémon games, Pokémon Red and Pokémon Green. It took four years longer than the original release date.

Still, there were glitches, bugs, and errors. The artwork in the game (e.g., sprites) needed to be updated to match the more refined artwork from the packaging and marketing materials, which was a big change too. Art director Ken Sugimori and the team had an opportunity to refresh the in-game artwork. Bulbapedia has some of the original artwork in that first iteration of Pokémon Red and Green. 

After eight months of polish, the refreshed Pokémon Red and a new Pokémon Blue came out in Japan. Red and Blue would be the versions of the games that made it to North America as well. Here’s a before/after comparison at Reddit:

While Charizard looks a little rough, none of the Pokémon looked that far off at first glance. That gives us a sense of how minor the polish was. (Rhyhorn looks literally the same!)

It reminds me of how the original Kirby also needed a year of polish, although developer HAL and Nintendo decided to push the release date out and cancel pre-orders. Pokémon took more time than that, and still needed more polish. One of the leaders must have decided that Pokémon Red and Green were acceptable to ship in 1996, even amidst the rest of the bugs—which weren’t dealbreakers—and imperfect artwork. That decision worked out well.

Pokémon launched first and made it perfect later. One way to see this: the initial momentum from the release gave the team much needed money and energy to keep going. They would do this once again with Pokémon Yellow, a game where a Pikachu would follow you around. 

If you find yourself blocked by perfectionist tendencies, maybe this story and approach will be useful for you.