Does anyone not do flat bench and just do flies? Or does anyone make their main exercise flies? ...I know when I do flat bench press it usually hurts my shoulder and I don't see a lot of good results from it so I was predominately doing incline, but should I switch to making flies my main movement? Thanks!
I switched from presses to just flys decades ago, for both reasons you've mentioned-development or lack thereof, and shoulder probs from BB. Felt strange to leave them out, but only for a very short time, and was definitely better for me in terms of development and reduced/nonexistent shoulder stress.
Before giving up on presses it's worth trying alternatives that can be easier on the joints and arguably better on the muscle-machine or DB presses or even pushups. I make flys the main course but then sometimes include some of these after, or just leave it at flys only-flat, incline, decline. I believe Bob Chick also does something like this, for the same reasons.
And of course take the time to always ensure a good warmup including a couple of minutes of windmills coupled with light sets and no more than a minute between sets to keep the area warm.