Every basement band started out sounding bad in a garage with the door shut. Open the door eventually.

Practice in private is where you get good enough to be heard. It is also, if you stay too long, where good work goes to sit forever, because private work never meets the thing that improves it fastest, which is a real audience reacting in real time. The closed door protects you from information you need.

Give the private phase an end date. Book the open mic, put the demo somewhere, invite six people to the garage. You hear your own work differently the second there is somebody in the room, and that hearing is worth months of rehearsal.