This movie gets poor reviews because people don't understand what it's really about. But let me start from the beginning.
This is an action adventure animated movie aimed at somewhat older-ish kids, preteens and teens. It does have a somewhat liberal spin on it (biracial family with a homosexual son), strong female characters, and there is a "dad doesn't understand me" trope throughout the movie, focused on the grandpa, dad, and son. Although the inclusivity of this film seems to intentionally poke the (conservative) bear, my interpretation of this was that, "America, this is you." Other reviewers criticize that the characters and their story have no depth. But everything these characters do is predictable because that's not what this film is about.
In the opening scenes we learn that Searcher (dad) discovered an energy source and decided to part ways with his father and develop it. So much that the community began to depend on it for everything. But now, that energy is running out. The whole movie is about the attempt to restore that energy source because the community has become dependent on it.
Spoilers follow
What they discovered is that the world they live on is actually a giant organism. Any living body is made up of many unusual organisms, designed to work together harmoniously. The body is designed to fight infection from intruders. Much as environmentalists talk about Earth as a giant organism, this movie treats Earth as a giant body, and all the creatures within it represent microorganisms within our bodies (e.g. the digestive tract).
The thinly veiled allegory here is that the energy plant that is killing the world in this movie is supposed to represent fossil fuels. Fossil fuels are killing our planet, and running out. We have become dependent on fossil fuels not only for cars and airplanes, but as a source of electricity. It powers our tractors, airplanes, delivery infrastructure, and even our coffee machines. Every industry relies on fossil fuels in our world just as the movie's world relies on these plants.
In the epilogue of Strange World, we find that it took about a year of living with no power before things could gradually return to normal and alternative sources of energy could be found that don't hurt their world.
Strange World attempts to start a dialogue about switching from fossil fuels to clean energy. But the message is so buried below the action sequences and uninteresting characters that most people have missed it, or maybe don't care.
Overall it's a fun distraction, seemingly designed to anger conservatives, but hits all the right buttons for liberals that are concerned about the environment.