We flew from IAD to DUB on Aer Lingus a month ago. Outbound was an A321neo LR/XLR and it was not bad at all. Legroom was fine (for me at 5'7"), big overhead bins should be required these days, and the entertainment setup was passable. The only complaint was flaky seat-back trays that required a real SLAM to latch. The damn things were constantly dropping down, getting slammed back not quite hard enough, and falling again. Not all of them, but enough it was noticeable.
Return was on their A330, which was noticeable worse in every way EXCEPT it's 2-4-2 seatings, so we had a pair of outside seats to ourselves, where on the A321, it's 3-3, so you have a neighbor in the window seat.
All these 2-4-2 are 20 year old aircrafts - seats are not slim. so less legroom. Airlines don't retrofit.
The -300s in use by Aer Lingus are a bit newer than that (but the 200s they use for west coast routes are in fact ~20 years old), but not by much. IAG has orders for 21 A330Neos, which, I believe, retain the 2-4-2 layout in economy.
Delta has 2-4-2 on their new A330Neos: https://www.delta.com/eu/en/aircraft/airbus/a330-900