Reading this makes me kind of sad because the industry right now wouldn’t support that. That author would get pushed right out, epub-only releases, less marketing, etc. I wonder if we’ll ever have a long epic like this again.
There is so much content out there that I don't see any particular thing as a "must experience" anymore.
HBO told the producers to take as long as they needed. I believe they were eager to jump to Star Wars and rushed to conclude the series.
See, at least the prequel trilogy of star wars had good ideas. It was just terribly executed.
The finishing episodes of GoT don't even have good ideas, in addition to being awfully written, lacking continuity, and poorly acted.
One of my favorite things was fans of the book series pointing out how Tyrion went from being the poignant observer of the universe through GRRM's eyes to simply being a sideshow dwarf that constantly said "my cock" and little else as soon as D&D ran out of book material for him. The "head vampire" trope for the NK basically meant I didn't watch the final episodes.
And Rogue One wasn't really that good, it was just "Battle Beyond The Stars", itself a cheap cash-in on the Star Wars craze, dusted off for Star Wars with some bad kung-fu movie tropes thrown in.
The real pain was people reading them when it came out, so they'd wait 2 years or whatever for the next book and then it'd come out and the plotline they happened to resonate with didn't get very far. Or it progressed some but didn't particularly end on a high-note.
The problem is that if you are at a point where even GRRM cannot move his own story forward, it's unlikely someone else will do a very good job.
And that's basically what happened. Even if the writers are the most top notch, they aren't GRRM, otherwise they would have their own fantasy series out under their own names, as opposed to writing for TV shows.
Epic fantasy is hard. Look at the middle 6 WoT books, almost nothing of relevance happens in 4000 pages. When GoT was signed I'm sure GRRM promised them that the next books were already "done" and ready for release but as is typical, 12 years later they had nothing. Honestly, they should have diverged from the source after season 4 and create a new story that could be concluded satisfactorily.