Flashbacks in Films

When I was a kid many films had flashbacks - and audiences didn't like them. You'd hear the groans from the audience when the screen rippled and the scene being watched dissolved into a previous happening. I believe Hitchcock might have been aware of this "problem" because the only film I can recall of his that had a flashback was "Stagefright"; but in that film the flashback was used for a dramatic purpose that was essential to the story - the murderer himself was telling someone what had happened so the flashback was a lie.
Flashbacks (and flashforwards) are used in the film I saw the other night: "Before the Devil Knows You're Dead", and while, to mind, they worked well since they were intelligently executed, I can imagine someone else feeling a bit uncomfortable with them. I think most people like a story to be told from beginning to end without the intercession of flashbacks - they stop the flow of forward action, hold things up, take one's concentration from one's involvement in the story, and interfere with that old "willing suspension of disbelief".
I recall seeing Kubrick's "The Killing" in a cinema many years ago when it came out first and many people in the audience groaned with disappoinment and annoyance when the flashbacks occurred.
Yet no one complained about "Pulp Fiction".
Well, "Pulp Fiction" may be the exception that breaks the rule; most films that use these filmic tricks are not popular with the general public. Often they achieve "cult film" status - as did "Memento" and "The Killing" - but they are hardly ever highly regarded.
Syndey Lumet's "Before the Devil Knows You're Dead" was not widley distributed (I saw it in an Arts Centre) and maybe the reason was the use of jumps in time - flashbacks.