I want to tell you something anonymously (for you), that I wouldn't say to you in person. You'd be insulted, and strongly disagree with me.
Have you spent the last few years working on your masterpiece game?
I can't guarantee this applies to you, but it almost certainly does:
Sorry, your baby is ugly.
I playtest other people's games frequently. Some of these games have amazing production values — expensive art, and painstakingly-detailed graphic design.
None of them are good enough to be published.
Here's the problem with your game: There isn't one.
You're a smart person, and you know games well. You've been working on the game a long time, and have considered every part of it. It's polished and balanced, and you've fixed all the problems it had.
Fundamentally, you can't see how the game could be any better. It doesn't have any problems. Therefore, it's fit for publication.
It's not that the game doesn't have problems. There's a reason why your game isn't particularly good, and it's a big reason, not a small one. The choices that separate the great games from the dross are often not something obvious, but a failure to understand something deeper about game design.
You made some fundamental mistake or omission in your design, and your polishing has served to cover up this wound. You wouldn't conceive of changing this thing about your game at this stage. You don't even see this problem, and you're only looking at the small details now.
You see the flaws in your game as necessary compromises, not as hard problems in need of a solution.
Playtesters don't love your game, but they don't know why, and it's too late to make fundamental changes anyway.
Even when a game idea is properly executed and polished, it doesn't necessarily mean it's a great game. Usually, it isn't.
You'll hear a lot that publishers don't want "good" games. They want great games! What they call "good" isn't actually good at all. It's your masterpiece, and so many other games like it — games crafted by seemingly-skilled designers, but not actually great games.
You probably have a group of people around you who "really like" the game. I've made this mistake too. I saw the people who liked the game, and wrote off all the people who gave polite "mixed signals" about the game. Many people have really low standards. Many people have no standards at all, because they've played very few games. Many people are polite. Many people like you as a person. You want to believe your game is good, so you see this feedback in the best possible light.
I've made "good" games, and I've made one or two great games. I now know the difference. Everyone likes the publishable games. People say "I'll buy this when it comes out" and out of nowhere "yeah, that [description] game's a really great game. How's it going? For the unpublishable games, no one ever said such things.
Until you get your game in front of a publisher, and they play it and reject it, you'll continue to believe your game is great. That's when you'll really learn this lesson, and it will be an important one. You won't learn this lesson from reading this article, because you don't think it applies to your game. Every person reading this article thinks their game is in that top fraction of a percent of games, that will be published.
Some people just keep going, trying different publishers, or other avenues for publication. They never learn this lesson, and eventually leave the world of game design. They forever imagine that their masterpiece game would've taken the world by storm, if not for the unfairness and callousness of the publishing industry.