The crop factor for APS-C (and smaller) sensors only applies, when using full frame lenses though. You can get a 16mm APS-C lens with an equivalent field of view to full-frame lenses, no?
The crop factor varies depending on the crop sensor. Technically the focal length will always be 16mm but it’s the sensor which determines the field of view. So even if it’s a crop lens it will still have a crop because of the sensor size.
Crop factor is still important with smaller sensors. I used to shoot with a Lumix G95(m4/3 sensor) and the 25mm lens made for it is actually a 50mm equivalent. Currently I shoot Fuji xs-20 (aps-c) and a 35mm made for it is the equivalent of a 50mm
