Arc welding without a mask isn't a smart idea. The whole idea of the mask is not to be able to see well. It needs to make almost everything dark because the intense light of the arc will BLIND you, and not just temporarily. After repeated or prolonged exposure you will quickly and permanently damage your eyesight.
Look, I get it. The masks are a real pain in the ***. They make working in tight places difficult and you might even see professionals go without them for spot welding. What you aren't seeing is the hours and hours they've spent with the masks on and that they're closing their eyes for the second or two the arc is going so they aren't actually exposing their retinas to the flash.
When I'm in the metals shop, I know where the arc welders are and I know how to use my peripheral vision to watch people instead of looking directly at their work without protection. If I'm observing their technique, you'd better believe I grab a mask. I hold it in front of my face instead of putting it on, but I still use the glass to shield my eyes.