The NFL, NBA, NRL, AFL, Nippon League, NHL, Euro League Basetball, MLB et cetera don’t have relegation, that’s the point. Organising your professional sport well is a good idea and has helped Irish rugby grow.
Maybe if soccer in this country organised itself better then it would be more attractive for punters to go to. Instead one Irish province in Leinster can get pretty much the same paid home attendance annually as the entire Premier and 1st Division of the SSE League of Ireland. And given that many of Leinster’s opponents are overseas, that says something. Fair enough the League of Ireland does have a British team in it, but at least it’s just a land border for away fans to travel over.