First, you absolutely know more than you think. Human beings branch out in adulthood and it is
impossible to compare your knowledge to others. In contrast to being in middle school and measuring your knowledge in universal scores in all "subjects" taken by everyone. You are not confident enough because there is no universal score like in middle school. When you have to work, or meet with someone with the same area as yours, you will feel confident. I am sure that happens.
Second, it's an unfair world. Some people have more time to put into stuff to think deeply and do work that don't directly, instantly lead to real-world impact. (There is one gentleman per neighborhood who "knows deeply" about French Revolution or Civil War, or so they think) I am sure Jeff Dean doesn't have a manager breathing down his neck. Have you tried going deep into something, and writing about it? Like Julia Evans' blogs on DNS? Why don't you try something like that? You mention Jeff, do you work in ML? Have you tried publishing research? It doesn't have to be NeurIPS or ICLR. Why not a small, independent paper in arXiv?
And, also, highly recommend a group of similarly motivated people for a study group. Because "deep knowledge" doesn't directly turn into product-being-admired-by-many-people, you might get bored while reading a 500 pager. A group helps the most.