Got bored, did research, Demogorgon can actually be blinded (kind of)
So I've seen a lot of people ask "How does the demogorgon get blinded? It has no eyes." I myself grew curious too, so I did research. Now, I'm assuming the Demogorgon doesn't "see" but "senses" the survivors using the petals of it's face. The Demogorgon is apparently sensitive to bright light; not as much as it's previous stages (Slug, Pollywog, Frogogorgon, Catogorgon, Demodog) but it's still sensitive to light. Judging by the look of the petals, they have the thinnest skin of anywhere on the demogorgon, meaning it's light resistance is less here. It's not being blinded by light, more of being blinded by pain. Add to that the sensors themselves may be light-sensitive and you have a Demogorgon that doesn't like flashlights.