You're right that Slick's songs are often the most interesting, but because of that they are somewhat hit-and-miss. I think her often strident vocals don't help when the songs aren't working (see "Eskimo Blue Day"). I think I let Kantner off the hook easy because he kind of writes the same song over and over, so at their worst they're just forgettable. Probably could have put "Twilight Double Leader" on here, although I think with a cleaner arrangement/production that one would be okay.
I only just realized that there's actually a "Worst Of Jefferson Airplane" album that's just an ironically titled best-of. So especially fitting for this prompt.