Is it normal that most findings in singing is found yourself?

I find that although I have had many teachers, some well known. I notice that all the major issues I had with my voice no one could tell me. Its kinda felt like a doctor visit where I go and tell them my symptoms and they sort of guess.

I learn tongue positions, mouth opening, breathing. However, a lot of the tension I had was never told. For example, I learned that I was pushing my voice and how important "balance" is in the voice as in literally you shouldn't think forward or backwards but the position must be stationary. I learned how I was formulating my vowels excessively with the jaw instead of just tongue.

I feel as though when I learned violin or piano these teachers drilled every possible factor to perfect technique. I feel like with voice teachers its more like throwing random shit on the wall until its useful.

I wonder if its the nature of singing due to the innate instrument or if singing pedagogy is just so convuluted.