Depends on the book, depends on the readers it is meant to appeal to, depends on how well it is done.
For instance, my first book started with a couple of pages of backstory. I sold it to the second publisher I sent it to, and it went on to not only earn out the advance but to bring in royalties for several years. And I still get fan letters from readers who loved that book. (Although perhaps—who knows?—it is possible that was in spite of the beginning.)
I was about to say that possibly the readers tolerated that slow beginning because that was back in 1989 and readers were more patient then. Then I remembered, the other book that went on to earn royalties over a long period was published far more recently, and also begins with backstory. My books that began more actively did not sell as well. Maybe I am more entertaining when writing backstory than action?
As a reader, I have myself loved many a book that began with backstory, if I liked the author's style.
Find out your own strengths, whatever they are, and play to them in the opening.