Sorry to hear about your situation. You are not entitled to any compensation from your insurance company or your neighbor in this situation. The first thing you should do is file a police report right away. If the authorities are able to identify who started the original fire, you could seek compensation from them directly or through the court system.
That being said, it’s always good to keep comprehensive coverage on your vehicle, even as it ages and loses value. Comprehensive insurance covers physical damage to your car caused by things such as fire, wind, hail, flood, theft, vandalism, falling objects, and collisions with animals. (You’d be surprised by the damage a wild turkey can do to a car and how often that actually happens!) The best part is, this is usually an inexpensive form of coverage that gets cheaper as the vehicle gets older.
If you’d like to learn more about comprehensive coverage, check out this article: https://getjerry.com/advice/all-about-comprehensive-coverage-car-insurance-by-cheryl-knight.