IMO, a big part of shitty reffing comes from the leagues deciding that new rules need to be focused on or that an existing one needs to be brought back to the forefront. You have a million things to look for on any given play — where there's fast action and a split second to determine what did or didn't happen — and then get new stuff on top of that that you have to pay extra attention to because that's what is getting someone above your pay grade all fired up.
A few years ago, it was head shots/targeting. A good thing to look for, but the rule was made so inflexible and wasn't equipped to consider factors like intent or an offensive player moving their head into the defender's path after he'd already committed to it. And if QBs are involved, it's even worse and anything that might kind of vaguely look like it possibly could have been considered improper contact is an auto-flag. End result: A detraction from the game because so many of those calls wind up feeling over-the-top in penalty in comparison to the actual hit. Worse in college where a guy can wind up missing four quarters of play over them.
And now, it's taunting for virtually no reason other than, I guess, fucking boomers thinking players showing emotion and having fun is a horrible example to set. It shouldn't take much thought to determine actual "IN YOUR FACE LITTLE BITCH!!!!!" stuff that's over the line, but for whatever stupid reason, it's been expanded so much that any display of in-the-moment emotion runs the risk of hurting a team. Guy on Iowa State gets dinged for, uh, slowing down on a TD catch, high-stepping a bit and looking behind him. Dude on Chicago got dinged for a sack celebration that involved taking steps towards the other team's sideline.
Only a total fucking pussy thinks shit like that's worth 15 yards, but the higher-ups in the league seem to fit into that category. Giving refs one more thing to not just look for, but focus their attention upon, for no legit reason other than vague-ass "protect the shield" optics. And because they're focusing on that shit, other stuff that is legit gets constantly overlooked. making the entire product worse.
Gotten to the point where I just take it for granted that there will be fuck-ups and there is a legit chance those fuck-ups will legit impact the outcome of a game, so all I can do is hope my team benefits from shitty reffing, as opposed to the alternate option.