I think everything has it's place. Down tuning definitely has a sound that, for certain situations, gets an idea across like nothing else. But Whenever I write, I tend to stay away from it. Some limitations inspire creativity, others inspire complacency. Early on in my youth I found myself addicted to drop D and played in nothing but that, recycling bad ideas. Stopped using anything but standard tuning, and found my creativity exploding. That being said, I also started writing more on the piano. So the increase in creativity could be completely unrelated! I will say that because standard tuning has been explored so greatly, it has a very "disguised" tonality. Could be anything. Many alternate tunings, open-tunings, etc., haven't been used for as many different purposes, and therefore have very powerful associations with certain kinds of music. I like that when I hear things in standard I don't immediately think of a singular artist or genre.
Those are my thoughts, for whatever they're worth.