A lot of the routing comes down to pressure around the tag `bicycle`. If there is a road illegal to bikes, tag it `bicycle=no`. But if it is unsafe, the best way to fix it is to better document designated routes, as well as cycleways.

OSM's philosophy on routing is you should not try to fix routing by trying to translate your opinion that it is unsafe to ride on the street into to tags. Instead the routing algorithm should improve or the data should improve to the point where an alternative route can be suggested based on data.

https://wiki.openstreetmap.org/wiki/Bicycle