I think of softshells and windshirts as two different classes of gear.
I consider softshells to be warm, often heavy, stretchy, breathable, water resistant garments that accel in high exertion activities like skiing or snowshoeing. Many weigh a pound or more, but they are made of very durable fabrics.
I consider good windshirts to be ultralight, wind resistant, breathable, water resistant garments that accel at blocking the wind and light precip. They add a surprising amount of warmth because of the evaporative cooling that they prevent. The lightest ones weigh only a few ounces.
I use a really light breathable windshirt, the Patagonia Houdini, which will repel light rain. I have never relied on it in steady soaking rain. Wearing it in a soaking rain seems to be different than most people's typical use, and I would fear the amount of energy my body would burn trying to dry it out again, particularly if it were windy.
I do occasionally use the soak-through theory for shoes. I wear highly breathable trail shoes and midweight wool socks. If I have a stream or river crossing, I just let my shoes and socks get wet, and then I walk them dry. BUT, I always carry one extra pair of dry socks in case they don't dry soon enough.