I never did well in elementary school music classes. I had no interest. My sister got the piano lessons. But, once I got into filmmaking I needed music for my films. I had listened to a lot of John Williams, Jerry Goldsmith type soundtracks, so I had fairly distinct ideas of what I wanted in a score, but I had trouble getting composers. A couple of people said yes, but nothing materialized.
Then one day, I dropped 2 grand on a synth keyboard and never looked back. I was like a one fingered typist. Then I discovered intervals - 3rds, 4ths, 5ths. Then I discovered that if I put a 3rd finger between the notes of the 5th that I could make a major or minor chord.
If you play orchestral or section type of samples/sounds, you realize that many instruments are mono-phonic (play one note or tone at a time, as opposed to intervals and chords). You might take that 5th chord and have trombones play the bottom note, clarinets playing the top note melody, etc. Of course, these instruments are in sections, so you can have a chord by having 3 trombone players each playing one of the notes. Of course, a timpani plays your bass note.
The bad thing is that this takes a while, but the cool thing about this self-learning process was that I had no intent on playing someone else's music, or practicing with well known songs. I was immediately making my own music. To this day, if someone asks me to play a well known song, it's not something I do. I literally have to figure it out by ear.
I'm sure there is a lot of good training to be had, and I think it can greatly speed up the learning process. I also encourage you to explore sounds and practice your own music, at home, to discover your identity.