Well, since I only really like lesbian porn (and occasionally some anal), here is my list of things that I cannot stand about bad porn.
1) Not so much now, but in the past some arty farty directors used to shoot porn in black and white. WTF. This is the 21st century. Not the 1920s Keystone Cops.
2) Slow motion. I mean what the f*** is going on here? If I wanna watch slow motion I'll stick it on my DVD. But I don't, so don't make that choice for me.
3) S*** directors who STOP an eager girl enjoying eating a pussy so she can stick a soulless dildo in the other girl's ass. Dude, you just killed the scene stone dead.
4) Again with lesbians. Directors who f*** about showing us a roving camera going round the room, instead of concentrating the camera on the pussy eating action.
5) Fake lesbians who shout 'oh yeah, f*** yeah' with such repetition it annoys me something rotten. Chicks like that shouldn't be in porn.
6) Chicks having sex on small couches, standing on one leg. In the most stupid poses.
Any more?