Ok so you're a realist, fine. But I'm curious, do you not think lucid dreaming is real? Or do you just not think it can be triggered with flashing lights?
I've had many lucid dreams, non of them involved flashing lights in my face. More importantly of all the methods to induce lucid dreams, flashing lights in your eyes isn't among the practices normally used in scientific studies. If it were actually reliably effective, it is highly likely it would be used in studies as a reliable method of initiating lucid dreams.
But as far as I know, lucid dreaming in general is not something that is being studied by a very large number of scientists, so we're not likely to find a whole ton of studies like this regardless of how effective it is.