Glad to hear you enjoyed your pilgrimage to Knock - imagine it’s only an hour up the road from me and I’ve never taken the trip up! Well, strictly speaking, that’s not true as I believe I was there a number of years ago as a young child, but I don’t remember it in the slightest! I’ve heard there’s a lot of “tack” being sold in stalls - such as glow in the dark statues of Mary etc., so I hope this didn’t affect you adversely…though I suppose all major pilgrimage sites are like this.
Ireland has so many lovely religious sites - Glendalough in County Wicklow (where St Kevin started his monastery) is beautiful and worth visiting. If you want a tough pilgrimage sometime, maybe you could try climbing Croagh Patrick - where the saint fasted for forty days and forty nights; also tough for the body (but good for the spirit!) is St Patrick’s Purgatory on Lough Derg.
Just out of interest - did you happen to visit Galway? It’s my home city and there are some lovely religious (and non-religious) sites - such as the Catholic cathedral and the Church of Ireland (Anglican) church of St Nicholas where Columbus is said to have prayed before he went on his voyage to the New World.