It is as destroyable as the smart disc initially was. When illfonic buffed the smart disk to be 3 instead of 1, they also buffed the HP of it making it almost undestroyable, making it almost impossible to win against good smart disc users, but they never buffed the ancient disc HP. In patch V3 they nerf the smart disc to the ground making it extremely easy to destroy, but they never changed the ancient disc.
So yeah, the ancient disc has remained as what the smart disc HP initially was, which I think is where it should be. The ridiculous HP buff before was too much, and the HP nerf now is too much as well. Illfonic being illfonic trying to balance the game