Couple of things, I don't think I've ever said they're going away on all lines. I said they have gone away on some lines. Regent and Seabourn have changed relatively recently unless on long voyages. I'm not sure Oceania and Azamara ever had formal nights.
Secondly, you haven't cruised in 7 years so you may want to before telling us how things haven't changed
And lastly, you've never cruised a luxury line so you really don't know how it's going to compare.