It's been several decades, about 20 different dentists, and I've tried everything they've advised, plus everything I can find. Different floss, salt rinse, different mouthwashes, toothpastes, brushing techniques, etc.

I still bleed.

It's my opinion dentists (like most doctors) suffer from dogmatism.

If flossing was the only relevant element, my gum bleeding would've changed over the decades - it hasn't.