I am part of the ratings decrease.
I can't answer for anyone else.
I have been watching FAR less NFL football this year, but my NFL football time has been dwindling over the past couple of years. A little of it is because the Rams, my team, has been about as pathetic as it gets for well over a decade. But it goes well beyond that.

Here's my reasons why I have made the NFL a far less part of my TV viewing, but with changes they can easily win me back:

The NFL product is simply not as good as it used to be. You younger guys probably don't even realize that. I think the lack of practice time, the inability to have more contact in practices, the inability for teams to develop their players with more off season activities has been substantially cut down by the CBA and it is really having its effect. The game is simply not as artfully played as it used to be, even 12 or 13 years ago.

The rules changes might seem pragmatic, but it has made fundamental changes to the game that are easily recognizable. And I don't like it. I don't like all the extra protection for the QBs. I don't like the ticky tack "touch a WR and draw a penalty" rules. Basically one of the biggest and best plays in football has become to draw an Interference call. I don't like the new kick off rules, moving the Touchback to the 25 and I despise the the PAT change. The defense is at more disadvantage than ever due to the new "tackle between the nuts and the nipples" rules they have instituted. I get why direct head shots cannot be allowed and are easily avoided. But just BREATHE anywhere near a players helmet (and especially that of a QB, and it's a foul.) The NFL has changed the game in ways that are a turn off to me.

BTW: I am fine with the new concussion protocol stuff and perhaps it needs to be even more stringent.

The number of games they play has not been matched by increasing roster sizes to allow for the additional injuries that are bound to happen. I understand the logic behind game day roster versus overall roster. But both need to be increased. I'd say a roster size of 57 or 58 and a game day roster of 51 or 52 would help substantially. Thus we see poor depth and luck of the draw decisions on game day as to whether to have enough players activated to fill in for any given position.

I despise the political correctness that Roger Goodell has injected into the NFL. I don't like the entire philosophy behind the highly played up Breast Cancer awareness week and then having the players wear pink to boot. Why don't we have Childhood Cancer week? MS week? Wounded soldiers week? Stop the atrocities in (fill in the blank) week? Downs Syndrome week? Heart health week? Because the special awareness campaigns that are chosen plays to a precise political party play or demographic and it is quite cynical. If you don't think LGBT appreciation week isn't coming, then you haven't been paying attention to Goodell's MO. Goodell has harmed this game tremendously. But he has also made the owners a lot of money. But the chickens do eventually come home to roost and I think they have booked their travel.

Not looking to argue with anyone about this. Your reasons for watching more, less, or the same amount of NFL are your reasons.
Just stating my reasons why my personal NFL watching has dropped by probably 80% over the past two or three years. And it has nothing to do with time or economic reasons.