There is a definite use for getting mildly buzzed as part of the creative process. Alcohol makes it easier to turn off the part of your brain that demands perfection and get a lot of stuff that may not be great but can be fixed rather than slowly trying to make one perfect sentence after another. Weed is great for when you need to sit back and stare at the shape of your whole plot and figure out how to get from where you are to where you want to be; surprising and wonderful connections get made. Then you put it down, and sober you comes back and finds the good parts. Weed is also pretty useful for visual tasks; it makes it easier for me to sit there doing fiddly details on a drawing without really seeing time pass. Sometimes it also gives me a power-up to my visual cortex and I can start tracing what I see in my mind's eye instead of the longer route of constructing stuff, but I don’t do that much as it’s perilously close to the point where I am too high to function. And then there’s people who claim that regular microdoses of LSD have lots of benefits for both general braining and creativity. Never tried it myself but I can see it helping.
You don’t have to get completely hammered to get useful creative effects. You just have to hit the bottle or bong or whatever hard enough to have some effect. And sometimes you can get in the groove without any chemical aid; that’s great! But when you can’t, and there’s a deadline... there’s mind-altering chemicals. Use them responsibly.