My lack of interest in the NFL has come from a few different things. I'm a Texans fan so some relate to it while others not so much. I happen to agree with the Kaepernick protest so my declining interest is not because of that.
1. Having to watch Brock Osweiler - he broke me after 6 games, can't watch anymore. I had Sunday off, chose to take a random mid day nap instead of attempting to watch him play football.
2. Commercials, there's just too many too often. It feels like these games take 3.5 hours so just like baseball, I'm out.
3. The league claims they're all about player safety yet makes every team play a game or two on Thursday which is just a few days after their previous game. The games suck, guys wind up getting hurt and I have no interest in watching a half-assed product with players having their career shortened by greed from the league. Also hurts that the Texans have the worst medical staff in football with the worst field in football. Some dude on a Texans message board without access to any patient files (only what is reported on twitter or the newspaper) has been better at predicting injuries and future complications than the Texans medical staff - often months in advance. But hey, keep grinding these guys into the ground.
4. Terrible selection of games unless you buy Sunday Ticket. If it's not an intriguing game or team, I'm not interested. Subjecting me to watching the Bears on a regular basis on local TV means I'll skip (sorry Bears fans). Putting any AFC South team on primetime should likewise be a fireable offense, such an awful division.
5. It feels like half of the big plays are called back for penalties. I'd rather wait for the highlights if everything is going to get called back.
6. The NFL's ridiculous discipline penalty scale. Beat your wife or girlfriend, get suspended a game or up to 6 (yeah right). Smoke too much pot, banned from the league.
7. Just the overall quality of the league. It just isn't fun to watch unless your team is really good but even then, it's a whole lot of blah. At least in the NBA most every team has one or two good young players that make them watchable, the NFL not so much.
Lastly and most importantly, the proliferation of the 3 yard passing game and never throwing more than 10 yards. I heard a crazy stat last week that Aaron Rodgers is now throwing 70% of his passes for less than 5 yards. He's one of the best QBs in the game but only 3 of every 10 passes attempted are longer than 5 yards. Boring. That doesn't even take into account how basically 80% of the league has turned into imitations of Alex Smith's 3 yard passing or throw it out of bounds strategy. I have no interest in watching games with rarely any possibilities of big plays.
Those are just a few of the reasons I've seen my interest decline. Oh yeah and Brock Osweiler, he's the biggest reason. He's the worst QB I've ever seen and yet my team is stuck with him for another year with a terrible owner whose family will likely never sell or ditch his crappy son-in-law GM. But mostly Brock.