It's a healthy debate as there's no definitive right answer. A large part of the decision comes down to where you are in the food chain.
If you're a hobbyist doing originals, or any jazz, it's probably not about the money. So reduced fee at Dog & Duck etc isn't too demeaning and feels positive if you're helping an independent venue scrape by.
Can see if you're on the tribute circuit - or where most full time musicians sit, my brother incl - sideman, corp gigs and teaching - playing for free is a different call.