Using the holes in a Ritz cracker as a pinhole lens to focus the sun on a sheet of paper seems eminently fine, as you're only subtracting sun from the case of looking at the paper outside (as opposed to using a glass lens to image the sun, which gathers light from more angles and concentrates it). It seems like poorer optical quality given its thickness, but could be handy if you don't have access to a piece of paper and a staple, or if you're a clickbait journalist trying to entertain a dying audience.

Looking through the hole is idiotic. It'll cut down on some of the light sure, but nowhere near the attenuation required - a quick search shows a #13 welding shade lets through about 10^-5 of the light.