I love Weezer unconditionally. Their major sin is longevity. If they had peaced out after Raditude, we'd be praising them for having a 17-year run with a whole lot of highlights. As tends to happen with older bands, they've become their own tribute band. They've churned out a lot of stuff since 2010 and most of it is disposable (though fairly listenable). Had it all been recorded as side projects, we'd just go back to "Pork and Beans" and wonder why they don't make them like Weezer anymore. And we could talk about how The Thermals and A Giant Dog and pretty much any band that's picked up a guitar in the past 15 years and done power pop, has echoes of Weezer.
As for most '90s Weezer song, that is immensely tough to pick. Literally anything off the Blue Album or Pinkerton is a good choice, and it might be the right answer to this question. I'd go with "The Sweater Song" because I went to that party more times than I can count. So that song is a transporter back to the early '90s for me, not to where I might have been when I heard the song, but the weird, aimless gatherings I went to where people would ask stuff like "Hey, isn't that one of the Meat Puppets?"