A lot of you seem to be overthinking things and missing the absolute obvious issue/contributor.
Ask yourself this question:
Why do YOU watch games?
Most likely it is for the some of the following reasons:
1 - You want to support your team.
2 - You want to see who wins.
3 - A team has great offense/defense and you like to see it operate.
There are others like maybe you like a star player or want to catch someone on your fantasy team but those are the main ones.
So why are those issues important?
Over time, the league has slowly but surely been shifting the rules to favor the QB. Remember that they were going to add entirely new rules to the roughing the QB definition, further decreasing the target area.
In the past, a very good QB with a great defense or a great run game, could beat an all-pro QB, but not really anymore.
If you want to compete, you have to have a QB. To keep a QB you have to pay up and that means stripping the team or filling the team with rookies in key spots. We managed a way around by bargain basementing our OL but ultimately 2 things happen:
1 - If you do not have a top 10% QB you have no chance, not over the long run. Since QBs are required to win, teams have to go all out for them. But since great QBs are a 1 in 4 prop at best (assuming you are terrible enough to get the 1st or 2nd pick), that means a lot of teams have to be terrible for 1-4 years just to get a competitive QB.
If you are a team without a QB, it can be easy to see that lack of a QB means lack of a future and quite clearly easy to give up caring for the year. All you can do is hope to be terrible enough to get a good draft pick.
2 - The sheer number of teams that have to throw in the towel early, means a lot of really worthless matchups. Usually you know before the game starts who will win, so why watch?
Admittedly, the loss of credibility in officiating and the loss of effectiveness of teams as teams are playing more raw/unskilled rookies and letting go of veterans for cap reasons, does affect the quality. But, since there really can only be 6-8 all everything QBs at a time, that means the rest of the teams are just treading water, or worse.
And if 6-8 teams are the only ones with futures, then why watch the other teams? They have so pushed the rules in favor of the QB that they have devalued almost all the other players removing much of the hope/enjoyment that someone gets a great player. Because great players that are not QBs do not really move the needle.