1) There are too many games. I don't have time in my life for Thursday night games or Sunday morning London games. Three on Sunday and then one on Monday is already stretching things. Moreover, many of these are gimmicky, like the Thursday night onesie battles.
2) Parity. The NFL wants everyone to feel they have a chance. So the schedules are generic and devoid of classic rivalries. Everyone plays on Thursday and Sunday night even if they aren't good games. And the league treats Jacksonville v. Tennessee just the same as if it were Denver v. New England. This is wrong. They should promote the best and bury the rest.
3) Too many games get decided by referees. The vagueness of the rules mean that on any play, the referees can call holding, defensive holding and (on any deep play) pass interference. These penalties change the outcome of the game. It's the rare offense that isn't forced to punt when there is a holding call. Defensive holding gives offenses four new shots, often for meaningless infractions away from the play. Pass interference lets refs move offenses to the one yard line late in games. This is the perfect cocktail of too much discretion and too much power for a sport meant to be solved on the field.
4) Too many commercials. The NFL has crammed in an amazing amount of commercials. They've invented new breaks. They now sell time that used to be used for analysis. TD... commercial break... replay of touchdown, mention of review... commercial break... extra point... commercial break... kickoff... commercial break. Give me a (noncommercial) break! It is now more likely than not, when switching between games on the NFL package that the majority of games will be at commercial at any given random time. How can you build interest when you aren't interested in showing the game?
5) Announcers suck. In the old days, the announcers were professional broadcasters who could report what they saw and spin it into a compelling story. These days, they are ex-players who barely know the rules, spew only conventional wisdom, and couldn't tell a story if their lives depended on it. The NFL wants to wow you with fame, when they should be looking for talent.
6) Too many injuries. Every game, some star goes down for half the season. It's not fun to keep seeing the game's stars taken away hurt. Half the teams even scapegoat their failures on injuries. The uptick in injuries seems to be the result of less conditioning practice resulting from the last collective bargaining agreement.
7) Bad play. Lack of talent creates sloppy plays, especially among the offensive line. The lack of development of quarterbacks means most teams don't have a legitimate shot. Even worse, there seems to be a sense that teams quit when things go wrong because they take the approach of "there are enough games that each one doesn't matter."
8) Fake stars. The NFL is letting players use sticky gloves that make average receivers into great receivers. They celebrate guys who have three or four good games as the second coming before they fade away again. They celebrate big fantasy numbers earned in garbage time.
9) No stars. Who are the NFL's stars right now? Tom Brady, who is as much a villain. Russell Wilson, who gets written off as too white. Von Miller who isn't well known outside of the AFC West yet. Ezekiel Elliot, who just arrived. Failing Andrew Luck. Failed Johnny Manzeil. Failing RGIII. Failing Aaron Rogers. Injured J.J. Watt. Injured abuser Arian Peterson. Their most bankable star right now is retried Peyton Manning. The NFL rushes to make stars. When it thinks it has one, it clings to them to the exclusion of all others. They need to cast a broader net.
10) Too political. Kapernick and his band of forty whiners hurt the game. But they weren't alone. The bureaucratic process for handling misconduct... the after-the-fact fines each week... the concussion industry... the spouse abuse games... the constant investigations and the legal maneuvering of union and owners alike. It strips the game of its fun factor and replaces it with the sense that you are watching a regulated product.
11) The No Fun League. I get that the NFL wants its players to promote good sportsmanship, but it needs to let the players have fun. The only "fun" they are left to have right now seems to be brutal hits, which feels wrong honestly.