Here is a paper which attempts to assess how Ireland has done since separating from the United Kingdom. It’s title: “The Old Connection Sundered? Ireland and the U.K. since 1916.”
The problem is that the only counterfactuals posed are the expectations of three independence-era economists. Which tells you precisely nothing, save that Ireland became neither a socialist country nor practiced strong import-substitution. There is no attempt to answer the question posed in the title: how would Ireland have performed had it remained part of the United Kingdom?
I am disappointed.