I disagree with a lot of the comments here. I simply can't stand "good" writing, esp. stuff written by people who obviously went through 'creative writing' courses. LOTR has long 'detours'. So what? We are being immersed in the best fantasy world ever, period.
My favourite book is the Water Margin... its numerous detours are one of its well-known features. I simply love all those stories within the main story.
Lovecraft was a racist. OK, but would you rather read Lovecraft or a dull novel by a contemporary author who abides by all the rules of political correctness?
Anyway, I believe the test of time is the best test. If Lovecraft, Tolkien, Leiber (and Poe, and Hoffmann) are still famous today, it is because their work is so great. I can't possibly find anybody alive today who is half as good.