I will disagree with everyone!
The best way to improve as a writer is to analyze how writers you really like, of books you really like, accomplished what they did.
Don't just read them, that quickly descends into story immersion and entertainment, you aren't really learning anything. You have to read analytically, you need to pick apart those conversations you love, and try to figure out what makes them work. Not just "you love them," but why you love them.
The same thing for exposition, or descriptions. How much did the author really say? Do they describe their characters in exhausting detail, or not much at all? How much is "enough" detail?
When they don't describe characters much, how did you get an idea of how they look? Could your notion of that differ from others?
How much do they show in terms of appearance, instead of telling you? For example, I can tell you Jack is very tall, or I can show you Jack is very tall by having him do something only a very tall person can do: Get something off a high shelf without tip-toeing to do it. Reflexively ducking to not hit his head on the door header. Accidentally getting hit in the head by a ceiling fan (I saw that happen).
How does that author start conversations? How do they end them?
How do they open chapters? How much exposition is used to describe a new setting? Count how many details they use. What senses do they appeal to; is it just sight and sound? How often do they appeal to smell, or touch, or the sensing of temperature or humidity?
How long are their chapters? A page is 250-300 words, measure it in pages.
How long are their books?
How long are their scenes?
All these metrics are things you should be thinking about, and should try to internalize and emulate, so when you are writing you are writing like what you already perceive is a great author.
Take notes. You will never learn these things if you just read, read, read for entertainment, because all of these things fly under the radar. You actually have to think about them to notice them, or notice a pattern.
When I first got the urge to write (long ago), I wrote some crap, realized it was crap, and taught myself to write by analytic reading of a handful of authors I thought were fantastic. I remember spending about a month going through just first chapters, trying to figure out how they opened a story. (Online resources did not exist then.)
There are mechanisms, and tricks they use to give readers "just enough" information to aid or trigger the imagination, without getting verbose and boring by giving too much detail.
Any online writing courses or advice you have read on story structure is all great, it can help you to identify those structures being used by your favorite authors. But if they really are good authors they have hidden the machinery of what they are doing, and to notice it you have to approach it with a mindset of looking for that machinery, instead of just enjoying the ride. Understand what is effective, and most importantly, why.