I used to be obsessed with Last fm when I was a teenager and was similarly obsessed with music in general. I think I moved away from it probably before my interest in music waned, if I remember right it was because something about the whole “quantify self” movement became off-putting to me. There was something weird about looking at the charts and who your top artists were the same kind of way having a top 8 friends on MySpace was a bit weird - I didn’t need or want to have these things explicitly ranked. I didn’t want to log on to Last Fm and view bands I’d been listening to like they were a sports league table.
It just wasn’t for me in the end but I can see how it’s appealing for other people. For me it will always be a nice little reminder of the mid 00s along with stuff like indie music and the mighty boosh.