i think some of it has to do with the lack of "star power" compared to the past. Think about the starting QB's in the league at the beginning of this year compared to 5 or 10 years ago.
Hoyer, Brissett, Kizer, Glennon, McCown, Siemien, Goff, etc., along with quite a few rookies that are not yet household names.
Combine that with the way every-down backs are no longer the norm.
I agree the anthem stuff is garbage and has hurt the ratings, but I think the product is a little stale at the moment as well.
It's not just a single factor causing the ratings decline but the anthem protests are perhaps the newest and most obvious one. Here's what I see:
1. Replay is slowing games to a crawl, and then the results of the replay are often guesses that can decide who wins or loses games just as much as the actual play on the field (does anybody even know what a catch is anymore?). This is a big problem in college ball, but an even bigger issue in the NFL.
2. Too damn many commercials. It's to the point where, college or pro, I let a lot of games get ahead of me on the DVR, and then catch-up by skipping the interminable commercials. It's ridiculous to have three min of commercials, have a kickoff, and then subject fans to three more min of commercials.
3. The CTE dementia issue is beginning to creep people out. It used to fire-up fans to see big hits and guys laid-out, but now it's just nauseating. I'm not sure what can be done about it, but CTE is ruining the game for some fans all by itself.
4. The product is boring and vanilla. What makes the college game so great is the variety of offenses one sees, the stylistic changes between teams, big plays, gadget plays, and so on. Right now, all 32 teams run the same basic offense, with all the rules tilted toward passing, and protecting the QB in the pocket (that rule about not tackling a QB low is just ridiculous, might as well put a red jersey on him). There's no room for variety in the game, all the imagination has been squeezed out of it. And the pre- and post- game shows are idiotic, too many people laughing and talking over each other, and just too many people on those panels to begin with. It's just a bad product.
5. The Anthem Protests. Alienating your fans in non-urban areas/red states is a bad business plan, that's for sure. I know more than a few people who refuse to watch the NFL until the protests are moved outside of game venues, where they don't belong (can YOU make political statements at your place of business? I sure as hell can't). It's died down a little, but I don't think an almost 10% decline in viewership can be ignored. In TV terms, that's panic territory.
Anyway, that's what I see going on.