It's not, ultimately it's just a medium to transmit something and each medium has their own merits and which you use is down to preference.

You are right, a more correct phrasing would be that generation was arguably the more or, imo, most significant.

The purpose of fiction can be for a lot of things beyond just entertainment especially how you view it. Plenty of my favourite works are ones I wouldn't even call entertaining myself but which I appreciate their thematic elements or commentary that they provide. Coincidentally you mention Verne and when contrasted with Wells you find that even back then, when it was known as scientific romance before sci fi became an established genre, you could see differences in story telling and their emphasis on entertainment or making some sort of moral commentary. If you continue to read sci fi you may find a work that you didn't necessarily enjoy reading but which the themes or elements alone will strike an accord with you.

My translation of Verne's work like 20k made for a more fun read than Foundation, certainly, but I still prefer Asimov simply because the post-war world is an era I'm more familiar with so have a better appreciation for the elements and issues he explores beyond Foundation, more so with I, Robot, and the context to which they were written compared than the stuff from the 19th century.

And, while you have an appreciation for Verne that's shared with a lot of other readers, the Golden Age as a moniker is generally a well established period to be from the late 1930s to the mid century where there was an explosion of authors so you can rightly praise Verne but sci fi readers wouldn't generally acknowledge the mid 19th century to be a golden age, let alone The Golden Age, because, as mentioned, sci fi wasn't even an established or recognised genre at that point and beyond big names like Verne and Wells you don't see a profusion of writers expanding the genre to the degree you see in from the late 30s.

You simply went in with wrong assumptions and expectations of sci fi as a genre, it's one that is more thoroughly rooted in its ideas than for its literary merit. If you're getting into fantasy and want to look at it's roots you can go back to milestone titles like Lord of the Rings that itself builds on themes and archetypes that go back centuries and millennia. This isn't so with sci fi where it's core is rooted more in its technological themes so generally its a genre constrained by time seeing as the industrial revolution was only a few centuries ago.

Foundation is part of the Golden Age sci fi starting around the cusp of the start of WW2 onwards, an era of unprecedented technological development. Major sci fi works of this era aren't known for producing much of literary merit, in part because many works were published piecemeal in magazines over the course of many years, they aren't cohesive novels in themselves as you are reading them today. What makes works from the likes of Asimov stand the test of time as a piece of sci-fi is simply that his generation were the first to reflect on this post war political climate where technology was being seeing as the driving force of societal development and prosperity so became key milestone works within the genre.

If you seriously want to get into sci fi it's probably better you read modern titles and work yourself backwards rather than chronologically unless you're prepared to do a bit of background reading to understand the climate of when particular works were written. Likewise with other milestone titles like Dune, the sci fi equivalent of LoTR; it's hardly good literature itself either but it's a milestone title because it reformulates the scale and depth of themes that sci fi is capable of being relative to its contemporaries that were being published that were still coming off quite pulpy.

If you would prefer something of more literary merit, I suggest you drop the classics and pick up The Book of the New Sun by Gene Wolfe written in the 80s; a sci fi tetralogy, starting with the Shadow of the Torturer, that is actually known for its literary merit.

I believe what you're referring to is typography; the arrangement of the typeface (font), size, line lengths, line-spacing, and letter-spacing etc in relation to the page space available.

As a collector of books from publishers that either have a history, or are still printed, by letterpress where exacting typographic standards are necessary to the overall broader aesthetic of the book; I do find it does very much matter. I have bought the odd mass printed edition over the years that have had awful typography; especially some packed story collections where the publisher tries to jam as much into the pages to save on spending money on splitting them into separate volumes thus making the entire text block jammed and claustrophobic that pushes right up the page edges with barely any margins for the text to "breath." An overall awful reading experience.

Some background would probably help a bit in interpreting LotF. There was a book called The Coral island.

written in 1857. The book follows the same premise, kids get ship wrecked and is told from the PoV of a character you may recognise as Ralph. They have an opposite experience to the kids from LotF; food is everywhere, they mange to fight off native Polynesian cannibals, help in some missionary work converting people to Christianity and generally bring order and have a easy time of it. This book was taught in British primary schools, the American equivalent to elementary school; it instilled in kids of the Empire the notion of what it meant to be of the superior western race, of being born in the land of hope and glory, and the kind of imperial order inherent in them that they should aspire to.

Golding, in actuality was a school teacher, so contrary to your belief that he never met pre-teens, he most certainly did and had very up close and personal experiences with them. These experience of what kids did is very different to the ideal, model imperial child that the Coral Island was suppose to be inspiring. The behaviour he saw in schools was also something that was intrinsic to the British social system. Class in Britain is something that in my experience people from outside Britain have a hard time grasping in how much it influences our lives here, it's not just a simple income classification, the social class you are born into essentially will dictate your life. Even as late as 2002, Britain still had one of the worst class divides in education within the industrialised world.

This is why the oft brought-up article about some kids in Tonga getting stranded isn't actually as relevant as many think it is considering the Tongan education system at the time of the incident wasn't steeped in the centuries old rigid social hierarchy of imperial and post-war Britain and all the kids in that incident were already friends of the same in-group and social class. Why does this matter? The grammar schools that Golding was teaching at weren't filled with working class children and had shared experiences of poverty; rather they were filled with entitled, petulant middle class kids.

In short, Lord of the Flies was a primarily a rebuttal to the Coral Island which was saying the superior western stock just inherently instils grand imperial order wherever they go; Golding was refuting that claim that kids when left to their own devices would just do what entitled kids do and run amok, start some fights as they wrestle between them to actualize, and very poorly at that, the imperial order they were taught and raised to believe in and, more than just being a commentary on the Conrad-esque darkness in humanity, that kids brought up in strict social hierarchies and upbringings would, again left to their own, go and start their own class wars amongst each other.