LA, Buffalo, Atlanta, Tampa Bay, Washington DC and Nashville are the cities in that article. The one that surprises me of those is Buffalo. That fanbase seemed to be pretty rabid and loyal. Maybe having what might be the worst team in the league is turning them off. LA has never really been a good NFL city, I'm not sure why the league has such a stiffy to get back there, much less with 2 teams. Tampa and Nashville are probably fed up with losing teams and are not really traditional NFL cities. Atlanta sports is a tricky one, the people tend to show up when they're doing well and competitive, which they've been for the last couple years, but that might be old to them now and the Falcons need to become crap again, then good and then the fans will come back. I wouldn't go to a game for the Redskins. My belief is Dan Snyder is the worst owner in pro sports. Every move he makes seems to be a money grab and doesn't give a crap about the fans or the team. The traffic to and from that stadium is ridiculous, the parking is very expensive, the tickets are too expensive, the concessions are way over priced and all that money goes into the black hole that is Dan Snyder.
Going to a NFL game is an experience. However, it's also a pain in the butt. You drive or take public transportation to the stadium, pay for parking, the tickets, and the concessions. You can add to that the drive, the traffic and the amounts of time those take out of your day or weekend. You get a much better view of the action on TV than you do at the stadium, no matter what seat you're in, and it's much cheaper and more convenient. Even with the blackout rules you can still find ways to see your team on TV or stream it on a computer.
Going to a game, tailgating and taking in the experience is a good thing and I believe everyone should do it at least a few times in their life. College and NFL games, baseball and basketball also. They're all a good experience live, but they are not a convenient thing to do. If the game takes 3 hours to play and you have to drive an hour each way to get there, add in the traffic component and other time consuming things involved and it's a pain to do it for every game. Even if you live in the city that they play in, you're probably not getting home from or to the event in 15 minutes or less, so it's becoming more of a TV event than live attendance event for many.
Just my 2 cents...your results may vary