I've never heard Demolition Man described as a grownup movie before.
If a movie is well made then it is as long or as short as it needs to be. If it isn't then it's not.
Movies you watch in theatres are one thing. It’s uncomfortable, you can’t pause it, you can’t contemplate it, there’s people all around you. It’s not an immersive experience despite a big screen.
So not all movies are best seen in a theatre. And the ones that aren’t are probably not long enough.