Flies are useless

Bodybuilders do them for extra hypertrophy on the chest. If you want a really big bodybuilder's chest then pressing alone isn't enough.

lol, no. Squeezing the chest when the arms are at the top of the chest is not the same as squeezing the entire chests so the dumbbells are pulled through the entire range of motion. That's like saying "squeeze the quads instead of squatting"

It's the same ROM as a bench press except the arms are kept straight. It's meant to put added work on the chest without having to use the arms.

It simply puts more strain on the arm and not the chest, more specifically the pectoralis major.

But I feel an intense burn and a great pump when I do flies, they are great.

You feel the intense burn because of the squeeze at the top which you can just as easily incorporate into a press. Watch this video to understand the myth of the fly: HOME CHEST WORKOUT MYTHS - The Chest Fly Fallacy!

While I can see KIND OF where you're coming from that's just too large a generalization to deem it "correct." 

I see no form of justification for saying it increases change of injury, let alone to say that is the ONLY thing it does.

 Possible advantages over pressing include greater tension, greater utilization of the pecs, possibly more activation of the pecs, the ability to access and assess weakness or more of a connection to particular parts of the muscle that are weak or lack activation, and they allow for arguably the best form of stretching your pecs that exist.

That's to name a very few. I can see the validation in having the sentiment you do to a degree but it's just silly to absolutely condemn a movement and say that another is absolutely useless or there is NO situation in which your compared movement is better.