Holy crap this is... not a good analogy.

Of course everything you do changes the future, that's causality. The point is you have no idea how anything you do will change the future, whether it will be good, bad, or irrelevant.

You don't want to randomly change your present by going back into the past because no matter whether you make it better or worse, any changes are likely to screw over you personally by making it likely you were never born so when you get back you no longer have family, friends, a job, etc. That's why we worry about it.