For how enemies spawn, building defences is actually a waste of time. They only spawn within your range, so if you occupy enough land with buildings that kick enemies out, you won't need any defences at all. Invasion's won't spawn enemies either. Also you are better off fighting literally anything that comes at you vs hiding in a building and letting them destroy it, it's not like we have any good defence tech (except maybe the bear trap things i just saw in the update).

Devs pls fix.