https://strava.zendesk.com/entries/95423147-Feedback-for-Strava-s-new-maps-OpenStreetMap-
Unfortunately many Strava users see this as OpenStreetMap being bad, when their complaints tend to be focused on the quality of MapBox’s imagery, the fact it disappears altogether at high zoom and the lack of streetview. To make things worse the tile style they used sucks. Its like a massive undeserved PR blunder for OpenStreetMap.
Had more thought been put into the transition it would have been an excellent opportunity to have a system setup to flag areas in need of mapping. Then provide mappers with Strava gps traces of the areas in question.