Biggest problem I have with a movie like this is them trying to make a movie out of an endless sandbox game. If a game has a definitive end, then sure it's fine. Just look at the Fallout show and Sonic movie.
Imagine if for some reason The Powder Toy suddenly became a huge thing and they decided to make a movie out of it. Where do you go while not being lame? That's how I feel about this upcoming film.
The problem with that is how they updated the end to add the end cities and other floating islands. If the end was just the dragon fight without the end cities like it used to be, I'd consider it more of a proper ending. Otherwise I'd consider it just like the warden or wither: a respawnable boss for a certain dimension. Though that's just my opinion.
I really don't see your point people have been playing minecraft in multiplayer, making stories for a very long time. There are TV shows dedicated to this on Korean TV. Kids love to watch those. There is every reason to make a movie.
And it might even bring up popularity in demographique that has never played understood the game
Go check out your local bookstore. There's plenty of minecraft chapter books already. Movies are a natural next step. In fact, Jack Black read the first audiobook in the series. It's pretty good.
Sandboxes are literally grounds for infinite creativity. Just look at The Lego Movie. No, if there's an issue with this movie it's that they aren't using the sandbox to its full potential, at least as far as our initial impressions can tell us. We have all seen every single one of the story beats shown in the trailer before in other movies.