Thanks for your comment! The particular cheese that you found (using mostly just the quad-shot so you can find a safe spot and wait) is something other people have mentioned, and will be fixed in a future update (coming soon!) With this fix, our goal is to make waiting in a single spot impossible - so that way you always have to keep moving and dodging bullets.
Also, destroying towers is another feature coming soon.
Stay tuned for that future update! Thanks :)