In industry goals are maybe poorly defined, but at least you have directions, and people that can answer the questions you may ask. If the contract is about creating a website, at least you know what you are going to achieve, even if you may have to fight with the customer to understand what he wants/needs on this website and what problem he is trying to solve.
Using the image of pushing the boundary: Doing a PhD is like wandering within some heavy fog. You want to push the boundary, but first you have to find the boundary. You don't know in which direction is the closest boundary as you can not see further than 10 meters from you. Maybe also the closest boundary is on top of a 8000 meters high mountain that you don't have the capacities to climb. So at the end you spend you time trying to figure out in which direction to go. Some PhD students may have supervisors that are guiding them through the fog, as they already explored the area and know it, but some other are on their own, trying to figure out a boundary to push that is accessible for them.
Situations of all PhD students are probably different, but this is my feeling about it.