Yes a simple base is 100% safe, however if you spend 90% of your time exploring/mining caves (I do), you will find plenty of danger. That's really the point of the game--not building a base that's going to be attacked by mobs.
I get this. My problem was that I'm not feeling an incentive for even gathering the stuff, since survival is already guaranteed and there are no further in-game goals. I guess I need reasonably constant and threatening waves of attacking aliens to keep my "games are meaningless, I am wasting my life here" instincts from waking up.
You really need to set your own construction goals. I had the urge to build a big house in a nice location. The I wanted to protect it, so I built a low wall around it. Now I want to landscape the hill that it's on. Next I'll want to irrigate and start a farm....