I agree that foot placement including position, angle and pressure are important, as is body angle. I have successfully climbed steep verglas in boots (no crampons) and ice axe, but this took extreme care to keep my boots flat and my weight over my boots. When I got to the top I relaxed and leant forward, causing my heels to lift slightly off the ice. I then descended rather quickly, eventually under control of my ice axe. When it is wet or slippery, progress needs to be more deliberate, ensuring secure footing in preference to speed.