I would recommend a feature to allow the game to auto-start another round. It can be walled off (auto-start gray is purchased with green etc.) but it requires a bit to much hovering over the game as it currently stands.
If there is not more interaction on a regular basis, there SHOULD be a way to further automate it, even if there is a delay that makes paying attention and manually starting waves more profitable. Say, a 30/60 second delay before starting another wave once you have purchased an auto-start upgrade..
It feels 'clunky' when the idea is to start it up over and over again to progress, and there is not much to do on a normal run but you have to almost stare at the screen anyways to restart it each time.