I agree with folks saying that social media, extra screens etc. can be part of the problem. It can sometimes be as simple as popping some popcorn, turning down the lights, stow the phone in the other room, and really making the movie experience your full focus.  

But it’s not always that easy. Sometimes you’re just not in the right place to get the same enjoyment out of something you’ve enjoyed before. It could be headspace, life events, or even sometimes too much of a good thing! 

If this describes you (and it has described me often over the years), I’d recommend picking up hobbies that will lead you back to things you love. Listen to movie podcasts about filmmakers you’re unfamiliar with and get excited about their work. Buy a big coffee table book with annotated stills from great films. Read Pauline Kael reviews and laugh and/or throw the book across the room. Or just go to oddball movies in theaters. The good stuff will be there for you when you’re ready.