I think today's casual fan would know Achtung Baby. And Joshua Tree. They are absolute classic albums that everyone knows. If they don't know those two albums then they can't even be considered casual fans. Those people aren't fans at all, they're just somewhat culturally aware.
You know maybe two Springsteen albums, and I'd hazard a guess that one of them is Born in the USA or Born To Run, both of which occupy the same space as Achtung Baby.
Anyway, I don't see why Depeche Mode can play a song but U2 cannot play the equivalent from their catalog. Both bands are of the same vintage, both had their commercial peaks at the same time, and both have a lot of hits and casual fans as well as a sizable contingent of die-hard fans. I find it really hard to believe that Depeche Mode or the Cure have fanbases that differ significantly from U2, yet they play so-called deep cuts and not only do the fans know them, they love them. U2 could do the same thing, and nothing from Achtung Baby would qualify as a deep cut, just as nothing from Disintegration or Violator would. Those are albums that casual fans have, just as casual Beatles fans have Sgt Pepper or White Album.
And yes, people still have albums. They buy them. They steal them. They listen to them. And never mind how many people have Achtung Baby in some form, Love Is Blindess has well over a million views on youtube. How many spotify streams? Last fm? It's not exactly Whatever Happened to Pete the Chop.
Maybe, but my local record stores are all thriving. HMV not so much, but the indies are always packed. With young people.