in the 80s they released six albums, that's respectable.
in the 90s they released four albums and had two mega tours. also respectable. wasn't ATYCLB supposed to be out in 99, too? that would have been 91-93-95-97-99, with two huge tours.
10 albums over their first 17 years is pretty good! the quality was consistently high, and they released a few classics.
to answer Bono's question from 1991, it all went wrong for the band when he got involved with jubilee 2000, and it's been wrong ever since. U2 are as good as Bono is committed to the band, and he hasn't been that committed. When he was a full-time musician, well, just put on any random song from 1980-1997 and it will likely be better and more creative than anything they've done since pre-millennium tension became post-millennium panic.
I can't fault Bono at all for feeling that his advocacy is more worthwhile than music making, but he's really got to to chose one or the other. it's not fair to the band, the brand, or the fans.
First 17 years: 10 albums, Bowie-esque stylistic changes, ambition, consistently good and several classic albums and songs
Last 17 years: 4 albums that are very similar, mostly mediocre and conservative, one classic to Rolling Stone and no-one else