Thanks for trying it out!
There isn’t really a downside per se to constantly shooting, however you can potentially change your weapon type to the lowest setting (which can’t hurt any enemy), in which case you probably wouldn’t want to be shooting at all and focusing just on moving and surviving the onslaught.
However, I don’t think we’d thought of it that way, especially since we were just basing it off our idea of existing arcade games, so thanks for the feedback!