But it depends on what you read. Take AI for example, it's trained on a ton of text right? It can write, but can it write effectively? Is its writing really "good" ?
The point I'm trying to make is, there's a difference between reading & learning from the patterns of what you read - and actually learning the best way to write - to actually provide a reader with maximum comprehension (If it's educational) or entertainment (If it's fiction/fantasy)
Best example I can give on this is - you can learn to swim from watching hundreds of people swim - but you won't be an Olympic level swimmer unless you learn from the best.
If that makes sense.