I'm surprised to find myself disagreeing with you so unreservedly on Superchunk -- an issue on which we have in the past been almost boringly in sync, to the point of my knowing with absolute certainty that you would, when I asked you, name "European Medicine" as the best song on Indoor Living.
I'll agree, up to a point, that lyrically, their later songs are no more "mature" than their early ones (although: "Phone Sex." "Art Class." "Silverleaf and Snowy Tears." Could you see any of these, just lyrics-wise, appearing on any album released before the mid-90s?) But I think it's pretty clear that their music has matured musically. Many of the early songs are little more than punk fragments, whose only obvious instrumentation is a few loud guitars and some drumming. Even the bass is barely audible. The guitars on the later albums -- I'm thinking of Here's Where the Strings Come in, Indoor Living, and Here's to Shutting Up -- feel way more textured, and you can hear the bass a lot better. Most important, there's a lot of keyboard-playing. And his voice is no longer screechy and indecipherable, but rather falsetto and quite precise.
This later style is not just different, it's more mature (and, I'd argue, better). It feels richer, more nuanced, more thoughtful, more serious. The albums feel like fully realized art works, rather than raw, tossed-off musings that they didn't have the patience to fully develop. These are all qualities that we associate with aging, and maturity.
Maybe you're talking more about style than substance here -- the jumping around, the jeans, the songs they choose to play live, etc. In which case, you know, fine. But I sense you're making a broader point...