Surprisingly, for once I agree with you.
Once Greenways have been built, rail will never run again, even if there are significant demographic changes (imagine if a successful multi-national saw Sligo’s population swell).
The same applies to other proposed Greenway projects like Midleton-Youghal and Rosslare-Waterford.
If the line is in a state where reopening is possible (and let’s face it Rosslare-Waterford could be reopened tomorrow), a Greenway shouldn’t be considered.
I also wonder if the tourism benefits are overstated. Authorities look at the Greenways in Westport and Dungarvan with envious eyes, but the unsuccessful one from Rathkeale to Abbeyfeale goes unnoticed. The first two are in very scenic areas; the latter covers unremarkable farmland.
Anyway, most cyclists I know would prefer to see the money go into urban cycling infrastructure.