I have a few things to say:
1. I agree with those who have said that U2 seemed suddenly old in the late 90s. I remember, on one of the first days of my freshman year of high school, in the fall of 1999 - a year and half after Popmart ended, over a year into my fandom, and a year before Beautiful Day and ATYCLB were released - in homeroom, we had one of those things where you introduce yourself to the person sitting next to you and you exchange answers to basic questions about yourselves and then recite them to the class, an exercise to become acquainted with your classmates. So, somehow, in my conversation with the person next to me, it came out that my favorite band was U2. When he was reciting the answers I'd given him to the class, he got to that part, said 'his favorite band is U2', and the teacher, a woman who I'm guessing was probably in her early 30s(maybe late 20s but whatever) at the time, twice the age of the high school freshmen in her class, said 'really? I thought they would've been old for you guys'(or something like that, I'm paraphrasing, I don't remember what the exact quote was), and another kid in the class piped up 'they are'. So yeah, teenagers in the late 90s just weren't that into U2, I guess, at least in the midwestern U.S; but I'm not sure that means older people weren't still interested - the teenagers that had been into them in the earlier 90s were in college by that time or even out of it. And this teacher, it turns out, was a fan too - she said her favorite LP was UF. She must've been an 'original' fan, a teenager in the earlier 80s, if she was in her 30s in 1999 and her favorite LP was UF.
2. To the point Irvine was making(and that many others have made) about Pop not having a big song to kick it off - I'm just going to say something I've said multiple times before: I often wonder what would've happened if U2 had held on to HMTMKMKM and put it on Pop instead of giving it to the Batman Forever soundtrack. It was a big single when they did release it, and I think it could've been a killer lead single for Pop; things may have been different.
3. For all the talk about how they strayed too far with Pop, in Please I can hear the band that wrote Love Comes Tumbling and Bad; in Gone I can hear the band that wrote New Year's Day and Until The End Of The World; in If God Will Send His Angels I can hear the band that wrote I Still Haven't Found What I'm Looking for. Etc. Underneath everything, the same band is there. For me, anyway.