Have you ever made pie crust from scratch? Pie is one of my favorite foods, but when I first learned how to make it, the process was extremely perplexing.
First, you mix together the dry ingredients: flour, salt, and maybe a bit of sugar. Then you mix in cold, cubed butter and use some tool (your hands, a pastry cutter, a blender) to make sure the butter is "pea-sized."
In other words, it looks nothing like pie crust. It looks like a bunch of little lumps sitting in a pile of flour, which is what it is! Hard to imagine how this is supposed to result in deliciously flaky, buttery pie crust.
Now for the metaphor: the design process often looks like you're doing something completely random that can't possibly work, because what you're doing right then looks so far from what you're imagining as your final product. You're imagining this super polished, functional, delightful product that millions of users rave about. And instead you've got a bunch of post-its, whiteboard sketches, and maybe some weird-looking monochromatic wireframes.
You can follow the process and know it will work out. That doesn't mean you don't need to know the why behind the steps - it's actually crucial for preventing disasters.
For example, if it's a warm day and the butter starts to melt into the flour, you should stick the entire bowl in the fridge or freezer immediately. This will make the butter cold enough to work with again. And why do you have to preserve those bits of butter? Well, it evaporates in the oven and creates air pockets between the layers of flour, which is how you get flaky pie crust rather than a solid mass of flour and butter.
Likewise, if you know that one of the reasons you're creating low-fidelity wireframes is so that you can catch any usability issues up front, you can immediately use the feedback you get to redo the wireframes, or go all the way back to the ideation phase if necessary. This might take more time up front, but it sure is less costly than finding out after you've implemented the whole thing.
So: process is extremely useful because they're a set of steps you can reliably follow. But to really take advantage of process, it's crucial to learn the principles behind them and to be able to adapt as you go.