Most of you have got it all wrong.
U2 should never tour with old songs, just for the tours sake, like just about any other older act out there, like Rolling Stones, KISS, Madonna, McCartney, and so on. They travel with nostalgia and old songs, like a cover band of themselves. It's painful to watch.
U2 gets a narrow pass for 30th of Joshua, because the album was such a worldwide monster. But they can't ever do i again.
U2 make new music for a new generation and tour it. Look at the set lists for SOI and SOE, for SOE all Joshua songs were even banned. Not playing With or Without You is like The Beatles not playing Yesterday. Ballsy! Like U2 should be. Their set lists have always been heavy with the current albums songs, like it should be.
Also, if the fan base is aging, the average age should be around 50 by now. I'm 38 and I've seen all tours since Popmart. I keep feeling older, on SOI (in Paris) and SOE (in Madrid) I felt surrounded by kids and I loved it. That's how a U2 concert should be. Joshua 30th (in Brussels) had an older crowd it seemed, and I still think they should have celebrated the album with a cake video on Instagram or something instead.
Either way, the next album I hope is cutting edge for 2021/22 and highly relevant, listened to by the kids and on top of the charts. It's the U2 way. If they can't make that happen. Retire. Touring with ancient songs is painful and would be a terrible ending for them. They would still make money, people would buy tickets, but it's like the Rolling Stones, Springsteen, Elton John or McCartney or other cover bands. Or they could just move to Vegas and do years of concert recidency. *puke*