That’s true of anything without a fly speed,
And without a burrow speed, and without a ranged attack, and without an ability that lets it ground all flying enemies. Maybe a skilled DM could make it work, but in other editions it wouldn't have been an issue.
Though the other problem is that you can deal limitless damage just by dropping sufficiently many 100 pound boulders. In 5e, they got rid of damage from falling objects, but you just need to drop enough creatures. Or ignite enough horns of gunpowder with a single Bonfire.