In general I don't think I'd be comfortable using any type of engine or framework which is solely developed by one person.

Let's say he goes crazy tomorrow and decides to camp on the beaches of Jamaica. No matter what you do, particularly with a closed source engine, you're stuck.

With unity if one programmer decides to quit, we still have a game engine that gets updated.

With Godot if both of the paid maintainers quit and the project collapses, you can just fork it and keep going.