How does one go about improving writing

By writing a lot, the untrained writer has gotten in a jam,
with nobody to give feedback, positive or negative, he has practiced his good writing habits, and the bad with no concern for the reader or the Judges,
and now that he feels more prepared and semi-ready to be seen and read, he realizes
he is a writing ascetic, a hermit, hoping to be a celebrity, small and big.
But how does one go about improving one's writing? How much feedback is needed, and at what level,
does a fiction workshop help with non-fiction writing or are they different worlds, unbridged and afar and all the skills he needs are unrelated and hard what if the years of writing he has done
0h the millions and millions of words he has written do nothing but re-en,-or a his bad habits and intuition and by the end of it he's come out a worse writer than before? But the one strength of his, that's underestimated,
his ability and willingness to learn and struggle until he improves and gets to be near the best the destination is not important, the Journey matters and tie's strapped his boots to take the trip
full of unexpected turns and the beasts and the critters a hard road ahead it will be that I understand I'm willing to put in the work according to the situational demand!