If one wants to learn, for example, algorithms, one does not need to do this in a self-directed manner. Several learning paths already exist. If one is having trouble grasping a specific topic, sites like Stack Exchange, Stack Overflow, Reddit, Khan Academy, and YouTube exist for one to ask questions on. I have had many issues cleared up by reading through previously asked questions, including seeing the person who a theorem is named after answer the question. Is it quicker to ask a teacher a question? Yes, of course. What will lead to longer lasting learning? For me, it's figuring it out on my own.
Eventually, one will come to a point where there is no longer an answer key, a teacher to guide you, or a well-worn path to follow, what happens then? People need to learn on the job all the time. Learning how to formulate a question, find the resources to help answer that question, and determine if what you have found answers the question are all key skills people need to learn. It helps to do this in a structured setting, but can be learned through the internet.
If self-directed means some people are not good at working without deadlines, then they can form a habit. Set aside time and work through some of the above material.
Cal Newport has put out many articles, blog posts, books, and now a podcast on how to learn and be a good student. I'm sure there are many other resources, including the soft-question tags on some of the previously mentioned websites. Old "Ask HN" posts are also a phenomenal resource. So, I think those who are not good at learning on their own really do have a tremendous amount of resources out there. Will some people even after using all of the resources still fail to learn, I'm sure some will. I think many people, myself included, aren't putting in enough effort to really find their limits, or to discover a process that works for them. Yes, for some people they can figure it out, others will have guidance from teachers, friends, or family, but for others many resources exist to learn the process on their own. At the end of the day, it's easier to go on Tik Tok than it is to crack a textbook and grind problems.
Learning requires work. There's no shortcut. And people who don't want to put in the work will find endless excuses. Just like there's no shortcut to playing a guitar like Eddie Van Halen.