Is baking by weight really more accurate?
Is it more accurate?  ABSOLUTELY

Does it mean that you can still follow a recipe by weight exactly and expect perfect results everytime?  No

You're right in that humidity will vary the weight, but if you're consistently working in the same area with a small change in humidity - its not something to worry about.  You'll adjust your recipe once and then generally stay in the same range.  Going by volume, you're always going to be all over the board.  Sometimes you'll pack light, sometimes tight.  Going by weight, you're going to be pretty close as long as none of the variables have changed drastically.

The problem you run into is when you change locations or the humidity changes drastically.    In the long run, you'll need to know what your expected dough should look and feel like.  After you've baked a loaf 100 times, you'll poke it and know if its too dry.

In addition to the feel of the dough, I have a hygrometer in my kitchen.  Keeping an eye on it lets me know if I should expect to need to add more or less water to my dough.  I bake A LOT, so I keep an eye on this to make life easier.