If you want an experience similar to how the movie was intended to be watched then you definitely need a couple thousand. Most movies are filmed in 4K, so you need a proper projector and screen size to even see a difference in resolution (I’d say 100 inch minimum). And it needs to have Dolby Vision HDR10+ support. Then you need a Dolby Atmos setup with a compatible receiver too. 5.1 won’t cut it with most movies. It’s definitely worth it if you can afford it. But if you can’t afford it, a theatre is still the only way.

Or you just watch it on your soundbar and your 50 inch TV. Or on your phone even. But then you’re not the target audience of cinema anyways.

Movies have become like chewing gum. A commodity that you consume casually and every day. Watching a movie used to be special. I used to indulge in movies, get completely sucked in on the big screen with big sound. Just think of all the great movies from back then and compare them to the commercial Netflix slob from now. 90% of movies I watch today are movies that were made 10 years ago or older. People think that theatres are outdated have never expierenced real theatric immersion.

They will stay relevant unless you have a 10k home theatre at home.