Internal combustion engines are more important than just cars. They enabled powered flight. They enabled heavy construction and mining machinery. They enabled plenty of other high-impact things in our lives. And at the very least, they don't stink as much - towns eventually drowning in horse manure was a real fear in the times just before the first automobile.
That said, we're now on the verge of switching most of ICE uses into electricity, which can be made more renewable than horses. We'll be good, if we can make the transition.
