Jane Austen's works were actually pretty fast paced for the time period, the writing norms of that time are just completely different then what we see today. You've probably already seen a few changes in writing style in your life time (I know a lot of new books during the 2000s-early 2010s had text lingo written in, now that's considered out dated). The fact that you can see flashes of brilliance even though her books are centuries old show that she was a great writer.

It seems you're confusing good literature with personal preference. I personally don't enjoy Faulkner or Steinbeck (hated east of Eden and grapes of wrath, as I lay dying was super morbid and a waste of time for me) but they are inherently outstanding authors because of how their books impacted people when they were published and how they continue to be relevant to people today (very few people know what the great depression was like but people can still get lost in a pilgrimage of a family trying to survive a hard time).

Aismov's foundation might have some antiquated writing techniques or prose but try to listen to how other people are reading and understanding it. They might point out something that proves why it's an enduring piece of literature. If people didn't gleam something from it, it would have been forgotten and would not be considered the classic people deem it to be.