I [historically disagree with Frederik on this][1] but will be good and refrain from downvoting him just because I disagree ;)
Where you have a situation where
> the station buildings, the railroad, the bridges and tunnels are still visible till nowadays
then that's an "abandoned railway" in aggregate. And OSM has always mapped in aggregate: we're happy for people to map a "primary road" rather than requiring people to micromap every single physical attribute. Yes, as often with OSM here, OSM, it's a spectrum: an unused viaduct followed by a cutting with an old platform is clearly an abandoned railway and worth mapping as such; an indiscernable route across a ploughed field might well not be. (_But_ as ever note that some people are more attuned to finding traces of old railways than others, and "well I can't see it and my opinion is paramount" is not a valid reason to delete things in OSM. We are not Wikipedia and we do not have a notability criterion.)
So: in this case I would indeed map it as railway=abandoned. The fact that services never ran over the line is largely immaterial; we don't map historic service patterns. We map what's on the ground, and if someone turns up and sees this, they'll see "ah, an abandoned railway". OSM should accord with that. The rest we leave for a history book!
[1]: https://lists.openstreetmap.org/pipermail/talk/2015-August/073804.html