highway=cycleway means “this is a cycleway”, i.e. it’s safe to assume it was constructed to cycleway standards.
cycle.travel routes over highway=cycleway and users are happy. The only two challenges I have are (a) differing expectations on surface (in Europe it’s mostly paved unless there’s a surface/tracktype tag stating otherwise; in rural areas of the US it will often be crushed limestone or similar), and (b) very occasionally people tag an MTB trail centre with highway=cycleway and no surface tags, but that’s clearly a tagging error.
Believe me, compared to the world of hurt that highway=path brings me, highway=cycleway is blissfully simple.