The bible never said watching movies is a sin, the word movies never existed in the new testament or the old testament. Instead the bible teaches us we should select what we give attention to. The advocate which is the holy spirit that God sent, will always tell us what is bad and good. Philippians 4:8 encourages Christians to think about things that are pure, good, and worthy of praise. This means that watching movies is acceptable if the content does not promote violence, immorality, hatred, or ungodly behavior that can affect one’s faith.
Watching movies is bad only when we watch what leads us to commit sins, just like watch porn, movies that teaches us to steal or commit any bad act that is not pleasant in the eyes of God. If a movie encourages lust, pride, disobedience, or mocks God, then a Christian should avoid it. Christians are called to live holy lives and glorify God in all they do, including entertainment choices. When movies are watched with wisdom, self-control, and a clear conscience before God, they can be a form of relaxation without being sinful.
The bible said in 1 Corinthians 10:23 “All things are lawful for me, but all things are not helpful; all things are lawful for me, but all things do not edify”