Self-taught dev here, and I remember feeling similar things at a similar age. During a gap between jobs I wound up taking three online courses: Algos 1 and 2, and Andrew Ng's introduction to ML course (all at Coursera). This was just out of curiosity, I didn't have any particular goal or expectation for them. At the time I didn't feel like I learned any One Big Thing, but in retrospect the courses demystified a lot o…
I still got nothing out of NGs courses. I vaguely remember something about matrices, how to decide how many parameters to change when training, and some other very-vague understanding things. I don't really understand why they are "the gold standard", but I also don't do any ML "irl".
That said, if you want to understand ML stuff I learned waaaay more from Andrej Karpathy's famous video series. But I still found the old Ng course useful in a "ah, so this is what they teach in a college intro to ML course..." way.