I'm not sure what the most effective way to promote gigs is...but I'm very sure fliers are the least effective. They are expensive, take the most time to distribute, are completely untargeted, and in many cases, not even legal. They can be cool as art, though.
Me too, probably. But this rule points towards an eventuality where bars are full of musicians watching one another play. Because most everyone else is at home watching Netflix these days. I do think the evolution of the "scene" is the largest part of the issue. You can be the world's greatest typewriter repairman but you still won't get much work these days.
Here's my indefensible position, and I've been carrying this around for a while: bandleaders whose bands play in small and medium-sized bars and venues need to start insisting on electronic drum kits. It's even better if you run all the instruments through the PA and eliminate amps. I know, I like my amp too.
Live drums, and the acoustic chaos they create, are at the root of 95% of the volume and sound problems in clubs. No drummer ever soundchecked at the same volume he played once the set began. From there, every other player starts turning around and cranking the knob, and we're off to the races.
Use a good electronic kit and run it through the PA, and you have total control over volume and mix, and you can do whatever you need to in order to keep people from flooding out the door. How many times have you guys played an early set in a restaurant and, despite your best efforts, have cleared the place out of 8/10 of the people who were in there eating?
Or get a drummer who can actually play.