GPS traces can work well in situations where aerial imagery isn’t up-to-date with roads and sidewalks. ...
traces made with a smartphone GPS aren’t really going to do anything on their own.

Imagery and GPS traces are the way to map. Aerial imagery suffers from offset, and the GPS traces suffer of signal interference (bumping on objects). To map correctly you need both, not just one.

You don't even need to use a smartphone, you can use your bike head unit. And the GPS now are multiband/frequency and multi constellation. This increases the accuracy by a lot - just don't expect cheap chinese phones to have this.

Traces are the best way to contribute, because combined multiple traces on the same path are a very good indication of a path (and it's exact location) and it doesn't require extra work. Just put your device to save your movement and you don't need to do anything else besides upload it after you finish - You don't need to osm and learn how to use iD or josm or any other app. You don't even need to learn the tags. Just save and upload