For a detailed analysis you'd have to ask
Tom Shippey, or for starters read what he has to say about Northrop Frye in "Road to M-e" and "Author of the Century". In Frye's view there are five very general literary modes: Myth, Romance, High Mimesis (= tragedy, epic), Low Mimesis (= classical Novel, Austen, James ...) and Irony (among others antiheroes).
And LotR is just all over the place, especially in the middle three modes. In TH, our title "hero"
Bilbo is firmly low mimetic, and the book is mostly told from his viewpoint. The
Dwarves stray away from this, as do
Gandalf,
Elrond and the Elf-king (and the off-stage Necromancer) - but where to put those silly
Rivendell Elves? Touches of high mimetic or Romance are there, but sparingly, as seasoning.
That refusal to stay pigeonholed in one of Frye's modes probably accounts for not a little of the baffled rage of critics, who seem to have considered the only appropriate modes for "modernist" writing being low mimetic and / or ironic - assuming those critics were aware of Frye's view.
Another point might be that for TH, critics would condescendingly allow "fairy-tale" elements in a children's book (though TH in parts deviates from standard fare markedly). But to include such elements in a book aspiring to be written for a mature audience - and JRRT repeatedly stated it to be a fairy (or Faërie) story for adults -
harrumph! that just will
not do! (Imagine the most pompous donkey-synonym you have ever met, or seen on a screen large or small - Robert Morley was almost peerless at such portrayals - snorting this out disdainfully.)