> I’ve heard that to be a good writer one should also be a good reader.
Yes, but you need to learn to linger over the text. To read it slowly in order to analyze how all the different parts fit together, to critically examine the overall structure, to consider how you would have or could rewrite it, to drill down into even the choice of words and how synonyms could have changed meaning and interpretation, to re-read it over and over across the years to see how your own life experiences change how you read the exact same content.
IMO not many people are either built for that, or are willing to expend that effort. Even I stumble - a lot.