The nice thing about forgotten knowledge is that it's much easier to jog the memory and get it back than to learn it from nothing. You likely still use a lot of the fundamental concepts without realizing it.
I am someone who came from a non-traditional, self-taught path ~25 years ago. I did get some formal schooling in electronics, which you'd think was useless, but I can think of a few times solid digital logic understanding has served me well in the past, for example. On the other side of that, I designed some shitty databases early in my career! Understanding normalization could have saved me a lot of headaches when I was new.