You can parse text instantly too, just probably has a limit of up to a few words that you can perceive "at once" as you say. Editing a whole 3 pages at once is the same as saying in photoshop you can edit a whole magazine worth of images at once, you also can't.

As with anything the shorter the feedback loop the better. The difference being that an image has an information density which is much higher than text, "image worth 1000 words", and you can make sense of it easier.

If you want to edit lots of text and see if it flows well quickly, some other ways would involve mapping the textual representation to something we can perceive quicker. The same way sometimes systems will have different sound tones for different actions, making a skilled operator able to detect mistakes by "listening" to the UI. If you can represent textual changes in an aggregated visual form, you might get what you describe.

For example if you could make nice grammar produce a nice musical sound when "read" by a computer program, you could potentially assess for correct grammar quicker by listening to the whole thing in much less time than you'd take reading it.

That brings to mind the quadrivium --- the second part of the seven liberal arts:

Arithmetic: quantity.

Geometry: quantity in space.

Music: quantity in time.

Astronomy: quantity in space and time.

Back in my uni days, the student centre featured a painting which was a representation of a musical piece --- something classical, possibly Beethoven's Fifth. It displayed in space (or more accurately, in a plane), what was usually performed over time. The painting was more conceptually interesting than visually appealing, though I like the idea.

Whilst I think you have a point re: images, there are often those which reward a more measured appreciation. A "where's Waldo" type visual puzzle might be a more trivial example but there are images which reveal themselves over time.

There's also what works leave us with. Text ultimately conveys, well, textual or verbal information. Speech is similar. Both can deliver a mood, though that's not essential. Music on the other hand seems to me to be far more emotional. Images in their simplest form are literally iconographic, more representing something than portraying it, though with detail they tend toward the latter. (Plastic arts such as sculpture seem similarly iconographic, and of course, the original icons were often such portrayals.) Video and drama seem to me more related to music than texts, working on moods and emotions. That though is occurring to me as I write this, as well as the realisation that both often rely heavily on a soundtrack. In the case of opera or musicals, to a dominating extent, less so in a straight stage play. And of course, on television, there's the infamous laugh track to guide us in our emotional response to a sitcom, standing in for the immersive live-audience experience.

Back to the suggestion: the idea of being able to autotune a text, so to speak, seems ... possible, now or soon, with advances in AI, GPT3, and the like. But as rocqua said, far harder to take in at a glance as compared with visual or video arts.

watch the feature film 'Arrival' (2016) for an implementation.