Another way to consider the matter:
Christ told us in Matthew 12:30 that he who is not "with Me" is "against Me", and he who does not gather with Me, scatters abroad. Here He stated a principle - there is no neutral ground. Those who are not Christ's, are at least under the influence of the evil one. If they are not working with Christ to gather people to Him, then they are working to scatter - to move people away from Him. It doesn't even have to be intentional on the individual level - and often it is.
Apply this to the many aspects of our society and culture.
Who produces, directs, writes, acts in, and markets or whatever, the vast majority of movies, books, magazines, etc that flood our world today? Are they Christ's? Under His control? If not, then whose agenda is being promoted?
Who writes, performs, publicizes, promotes etc the majority of today's music? Whose agenda is being promoted? And what effect does it have on people? Does it draw to Christ? or away from Him?
And so one might go on. Should these questions not, at the very least, cause us to be suspicious of these media? And the extent we will allow ourselves to be exposed to them?
I am not concerned about theatres - they are buildings. When I was a kid, theatres were, but definitely, bad! (Unless they were being used for an evangelistic series!! - confusing to me as a kid - 1960s vintage.) This type of rule is not very helpful.
But the principles of God's Word are essential. In the last 40-odd years, many old rules have, thankfully, disappeared. Some persist. Sadly, in the process, they have not been largely replaced by a study of, and understanding of, Biblical principles, which would empower us, young and old, to make good biblical decisions about our choices and behaviors. Instead, there is a lot of "anything goes" attitude. And because of this, there is still a lot of argument about "rules". I don't see and hear much about principles...