I agree that there are many rail priorities that have gathered dust over time probably the most inexplicable one is failing to extend the railway to Navan from M3 as was the intention.
Railways are more than just about the star performing lines they are also about transport infrastructure in the society that lead to future development and economic options. Knock Airport was rubbished often in the initial phase yet today it relieves traffic from the west going to a clogged Dublin everyday.
Galway is looking for solutions to deal with traffic gridlock, the railway link to Tuam is an option - the link to Limerick is a success already.
You rightly mention Brexit , the WRC is a north South option that could relieve the overused mainline south from Dublin and give access to Rosslare and Waterford ports for the future.
Railway is a transport solution that will become more important why not use infrastructure that is already in place and owned by the state. I take your point on different priorities whoever sets them