D&D isn't even the most free form RPG out there, there are plenty of systems that run the gamut from "highly tactical and rules based" to "almost freeform colla

D&D isn't even the most free form RPG out there, there are plenty of systems that run the gamut from "highly tactical and rules based" to "almost freeform collaborative story telling." D&D at least has well defined combat rules. I've ran games that use cinematic combat rules, where the books have suggestions and some math, but a lot of things are left up in the air with the general guidance of "whatever is awesome." So there aren't rules for shooting grenades out of mid air, but it made for an awesome climax to the story as the team raced onto the escape ship and the hanger bay door was slamming down, so of course I allowed it. I was playing one game where we the players objected to how the military was prepping for an AI invasion so we rebelled, next session the DM brought in a giant map and it turned into a base building tower defense session. D&D can go off the rails, other systems can go off the rails then continue until things are off planet!