I used to think this way about prose too, but a book called "First You Write a Sentence" by Moran changed my assumption on this one. As Moran points out, the "sound" of writing conveys meaning in itself. A little flourish, so long as it's not distracting, can improve the clarity of a sentence and make it more pleasant to read.

Can't beautiful or entertaining writing also add a layer of enjoyment on top of the pure content?

You can see this in fiction books (e.g. The Lord of the Rings) and some technical content (e.g. why's (poignant) Guide to Ruby).

Beautiful writing is more memorable and more enjoyable to read and therefore you're more likely to read it, remember it, and be inspired by it. Hence invisible writing is not the aim, but I agree writing shouldn't get in the way of you understanding something.

The author of the essay addresses this point head on, and has a very different philosophy: "Those who read only to be informed and never to delight in the words on the page have every right to do so. But do not write for them."

I personally would have to strongly disagree that "the best writing is invisible to the reader." The best writing scintillates and sparkles, it begs to be read and re-read, to be read aloud and savored in the mouth like a sip of wine.

"This paper will challenge the distinction that is made in some quarters, but not in all, between use value and aesthetic value in literature and elsewhere, a view that restricts the realm of art and the aesthetic to a minor, often diversionary role in human activity. This view derives from the presumption that art is an autonomous activity set off from other activities and released from moral, utilitarian, religious, and other entanglements: it directs the mind to the idea of “art as such.” Such a divorce is, of course, an impossibility. No art and no theory of art ever conformed, or possibly could conform, to this standard. All art and art theory bleeds into the social realm, is contaminated with ideology, carries out moral agendas (however secretively), performs utilitarian functions of innumerable kinds, and hence can never be isolated from these enabling frameworks. Art and aesthetics can be aspectually isolated from morals and the rest at any point in time, and they have been so isolated from antiquity to the present. But there is no necessary reason to make this kind of separation. And there are further, possibly deeper reasons not to do so." - James I. Porter

https://classicalstudies.org/utility-aesthetic-and-aesthetic...

I wouldn't say the best writing is invisible. But writing is an instrument to convey meaning. A pretty tool which doesn't do its job is no tool at all; meanwhile, even an ugly tool can build something beautiful.

"Best."

The medium is the message.