On the level of the individual a working placebo is a success.
You're saying that my eyes straining going away from reduced blue light is placebo? I can feel it right away and it gets worse in minutes, time and time again. As soon as I remove blue light the strain is gone. Honestly, I don't care what other people have to say, to me it's obvious that it helps and I stick to it. Again, I don't think this is universal and it may not help you if you don't notice immediate improvement.
That's reasonable: it works for you. But be aware that, since placebo effects are psychological, their effects can be noticed in the time it takes your brain to notice you put them on.