My father shares your views, but in the South anyway, Sinn Feins success is due to the corruption of FF and the fucking non entity that is FG and labour.
The health service, high taxation/poor services, homelessness and the abomination of the housing market has driven younger voters who did not grow up in the troubles into SF. SF have also been clever an put front and centre good communicators with no historical link to the IRA. People like Mary Lou and Pierce Doherty are far more effective communicators than anything FG/FF have.