Let me answer your question shortly: the line between 'good enough' and 'over-polished' is hidden in fulfilling your main game mechanic. One easy way to find out the main game mechanic is by figuring out if you write in your notes "My game is about ..." and just fill in the blank. Trust your game mechanic and release it as a prototype, people will test it and let you know their thoughts. Someone told me before that he's a friend that developed a simple app for 15 years! So you gotta stick with your deadline no matter how hard it might be. 😌
We actually faced this challenge as we developed our game and I was lucky to have Senna because she was the brakes that stopped us from going into the endless loop of doing last fixes. If you're not a solo developer you can ask your teammate to have the "brakes" role. ☺️