It really depends how good the course is, with well-designed problem sets/project prompts you can't really fake learning (assuming you actually complete them). Is it going to be totally exhaustive of everything you may need to know in practice? Obviously not, but no single project will be either, especially not for such a broad field as machine learning.

Independent projects can definitely be a great way to learn, and yes many courses are shitty. But it is also very possible to take a good course and walk away with new knowledge you didn't even realize you needed. Some of my favorite projects actually started with an idea from a course, and then I learned even more in order to further expand on it. Synergy between project-driven and course-driven education can be a powerful iterative process.