Austen isn't as tedious as, say, Milton or Joyce, but man...she doesn't move the plot along quickly.
I could even finish the Cliffs Notes of P&P, just too painful.
Compared to whom, though? If you compare her to other writers of her day, her books do move more quickly.
A lot of what's in Austen isn't stuff that teenagers can really appreciate -- irony, subtle psychological observations.
It's easy to get really sick of Janeites or Austenians or whatever her fans call themselves, but her books weren't the worst or most inaccessible stuff in British literature. That's why they've provided material for so many adaptations.
FWIW don't bother with the awful British television series Lost in Austen, a real cringe-inducing modernization involving time travel, one of the worst of many bad shows Britain has produced.
Who IS a great writer of that time? Austen is one of the more economical writers. Not a lot of fat.