For one reason, AI images such as the one you're using for your game's cover right now often indicate to people that a game is low effort; games with AI covers tend to use lots of other AI assets (which it doesn't look like yours does), or possibly use basic game templates without adding a lot else to it. Even when this isn't actually the case, people are going to assume it about your game and not give it the benefit of the doubt.
Additionally, many image generation platforms take advantage of plagiarized art and are massively energy inefficient, and most people recommend avoiding them altogether.