For other topics that aren't strictly programming, eg AI, ML, game theory, cryptography, quantum computing, probabilistic methods, optimization,... it would tak

For other topics that aren't strictly programming, eg AI, ML, game theory, cryptography, quantum computing, probabilistic methods, optimization,... it would take a significant amount of dedication to match the amount of understanding that a rigorous course with problem sets can give you in self study. Also, you're going to have an extremely difficult time getting to work on that stuff without a degree, given that even PhDs often end up on regular business bullshit.