That's why you don't adapt a book with 200 pages of falling action. Once the dramatic question has been answered, almost everything else is redundant. Once you've saved the world, nobody really cares how you get home, and if anyone's moved the chairs, or if anyone use lft. You've got to wham, bam and finish. They had the same problem with Game of Thrones, once you've saved the world from the Night King, nobody cares who sits on the iron throne. The question is redundant. Jackson could've created a film where the question was 'will Frodo ever get back to the Shire' but that's not the question he asked, we didn't spend long enough there to care and we didn't give him enough stakes to return. If he'd asked that question, then perhaps we could've had the scouring of the Shire, perhaps. Probably not though. It's still a clunky addendum.

Perhaps in the theatre you could get away with it, but on film not so much. If Jackson had ended with the ring and gollum going into the volcano, nobody would've blamed him. That's the filmic ending point . I already applaud him for taking a book that's really about language, what sort of bread everyone enjoys, and what the grass looks like and injecting enough excitement into it to make the film bearable. It's one of the few examples where the film is infinitely better than the book (controversial opinion I know) - though he properly jumped the ego-shark with The Hobbit.