Game designers avoid creating perfect games for a few reasons. Firstly, having a perfected game removes any potential for player growth and experience. If the game has no flaws or challenges, players will quickly lose interest and move on. Secondly, part of the appeal of games is the sense of accomplishment that comes from overcoming challenges and difficulties. A perfect game would eliminate this aspect entirely. Thirdly, game designers need to balance mechanics, depth, and width in order to create a compelling experience. If a game is too focused on one of these factors, the overall experience can suffer. A perfect game would likely lean too heavily on one or two of these elements, resulting in a less enjoyable experience for players.
