You’d die on a mountain bike on actual trails.
The one time I did proper mountain biking on designated trails was when I was in school and a group of us boys went on a week-long "Army insight course" and one of the activities they made us do was mountain biking
The army guys had obviously been to this place before, and they made us go down this really steep straight hill very fast, and at the bottom it didn't level out onto the flat part, there was just a sudden drop where you were meant to pull up and do like a jump off it. Of course nobody knew this so we all went steaming down this hill very fast and racing ahead the first guys to reach the bottom didn't know to pull up and they just went front-wheel first into the ground and all faceplanted over the handelbars
Looking back, someone could have got seriously hurt, but it was funny at the time