Cycle route networks are pretty much sui generis and need individual parsing.
I think you could say that the ncn networks in the UK, France, Germany, Denmark, Switzerland and the Netherlands are pretty much of a piece. Then you have countries like Spain and Ireland where there are a handful of individual routes of varying quality, but parsing them as a “network” isn’t going to work. Italy’s kind of between the two.
The US Bicycle Route System is something different entirely, largely as a result of America’s love affair with the automobile and its system of government. (I have a comment saved somewhere from a former Adventure Cycling Association intern explaining why Missoula has half a dozen cycle routes passing through it and Denver has none.) Applying European ncn assumptions to the US really doesn’t work. Australia applies ncn to motorway hard shoulders, which is the sort of nonsense that cycle.travel enjoys snuffing out with extreme prejudice. And so on.
icn routes are even more uneven. EuroVelo is EuroVelo and that’s great. But then there are medium/long-distance touring routes which are akin to European ncn routes but just happen to cross a border: the Avenue Verte, Munich-Venice, Via Claudia Augusta, Alps-Adriatic, etc. I find it difficult to justify giving these any degree of importance above ncn routes.
rcn and lcn… let’s not go there?
One thing I would like to see is more use of type=network, network=bicycle relations. Fairly often you’ll see a city’s favoured bicycle streets mapped in one unholy multilinestring of a route relation just because it renders on OpenCycleMap. That’s really not doing anyone any favours. It’s not a route - let’s not map it as a route.
Ultimately, just as with anything in OSM, specialised renderers/routers will benefit from more granular information about a route. But the broad-brush classifications are probably still necessary for data consumers who take this sort of stuff less seriously.