> Reduce the reflections
Overuse of reverb is an obvious sign of an amateur production. Unless you’re going for a specific special effect, reverb is best used sparingly, as it can overwhelm a mix. You can simulate a single soundstage by using a single reverb on an effect send, and applying different amounts of it to each instrument to suggest its position in this artificial space. Also, our ears get inured to the sound of reverb over time, so take regular breaks, or assume you’ve used too much and reduce the reverb after a lengthy session.