I don't know if its a good movie, but it left me with that tight feeling in my gut one gets when you have this "Oh crap, that could actually happen irl" moment.
As the title says, the movie is about acid rain where climate change has made it so acidic, that it can burn through skin, roofs, cars, pavement etc. It's not explained how it happened, only that it occured in South America first.
Anyway, what made it so frightening for me was how inevitable it is. You can fortify places against zombies. You can escape from radiation underground or in places of the world that didn't get nuked. But with this acid rain, the world is basically fucked.
Everywhere it comes down, the place is basically dead land because everything gets contaminated with acid. The plants, the animals, the water, everything. As an example, during the early part of the movie, we see characters falling into a very large river, so the acidic effect should be diluted. And even then the water was immediatly burning their skin and made their bodies smoke.
And you can't shelter food and water eithrr, because the movie shows how the rain melts regular rooftops within a day. Metal and stone seem to be more resistent, since cars are shown to be standing in the rain for hours without melting, but, as we know, constant dripping wears the stone.
So over time, all your self made metal and stone shelters will be eaten away. Same will be true for any kind of bunker, since the rain will eat its way through the dirt and reach said bunker eventually. And even if it doesn't, all the water on the surface will be acidic and all animals and crops will be dead or greatly diminished, so you will run out of supplies eventually.
It's by all means the end of the world.
Granted, the movie leaves it open, since it only covers the first 2 or 3 days of the event and doesn't show what happens afterwards or the wider state of the world. But given how inevitible rain is and how water manages to squeeze into even the smallest crevice, I don't see how it could end well.