>>212012589 (OP)A big part of the issue is that its used in an ideological fashion (and therefore kind of weird or nerdy) instead of just being something that everyone normal does, i.e. the popular thing to do.
Ireland has a ton of top-down promotion of Gaelic and not enough community involvement in proper towns. Welsh is doing proportionally much better because their core native speaking territory is contiguous and has actual community backing and immersion schools.
Overall if you want one single factor to look towards for language revival look at the number of students in TL-medium schools, then you’ll have a pretty accurate predictor of future speakers.
Welsh has a lot of kids in Welsh medium schools. Gaels have very little. Gaelic is dying, Welsh is growing substantially. So all it would take is the Irish government to actually take its resources and use it to found more Gaelic schools instead of teaching it as a secondary language.