I played a 4 hour show with my cover band, packed up and raced out to the burbs for my original band's show. That equated to about 4.5 hours with a bass on my shoulder. A heavy bass is just not an option no matter how good it sounds.
I totally agree with you that there are good and bad sounding basses regardless of weight.
I've done those types of gigs more times than I care to remember.
Schedule enough of those and one tries to get every possible advantage to make those evenings less gruelling.
For me, that includes lightweight basses, definitely. And lightweight amplification.
I've done a lot of things to diminish the savagery of those evenings. Lightweight gear is not the most extreme.
To each his own, though. Just sharing my reality.