The good teams still play it.. But high powered offense makes it hard on good defense. Sudden change all the time can be tough. 

22 hours ago, TimeWillTell said:

I think the rules favor offenses. You see too many pass interference calls in the games now. Which are cheap first downs with the offenses. I also think the spread over the last 25 years has evolved that you have to cover the whole field. Before then you covered a 15 foot box pretty much. 

Another factor are RPOs. People run them now and defenses play man behind it to  stop it. Creates matchup problems.

I see the same in basketball games teams scoring 80 points for 8 minute quarters? 

 

Spot on with everything here, and I think the bolded is the biggest factor. It gets harder and harder to play defense in football, on every level.