As many have said, back then the Beatles were everywhere, but there was always a veil, you didn't see them together in anything but a performance. There were no dull moments, no acrimony or anything less than a united front and certainly never going through the drudgery of being musicians working the creative process. By the time the movie came out the Beatles had broken up, and there had been advance press about the delays in the release. The prevailing sense in the public was that the movie was a chronicle of the band breaking up, and you got to watch your dream crumble before your eyes. It was certainly very difficult watching for me as a young fan - here were my heroes, rarely finding the spark, working separately even when they were together, Yoko haunting, John detaching, George tiring of having to claw through Lennon / McCartney for his chances to shine and so on. The rooftop concert was beautiful but it didn't wash away the awful feeling of watching the Beatles disintegrate, knowing that they'd really broken up for good this time.
There wasn't any discussion back then of the grinding schedule they kept, how and why they were brought back together for the Get Back project, or even what the project was and its ridiculous timeline. There are some very fine books that have come out in the last 20-30 years about the Beatles in January 1969, but there was very little in common knowledge back then. The bad feelings the different camps have harbored over the years kept the movie out of circulation after the mid-1980s and I think they all wished it would just go away because none of them had good feelings about how it portrayed the Beatles and they didn't want to revisit all of the bad that happened in front of the cameras. That was the whole reason for Peter Jackson's project, to provide a fuller context that would explain why these things happened and to offer the viewpoint that would be held as new parts of The Canon forevermore that the Get Back sessions weren't the horror we'd all kept in the closet. Mr. Jackson's project was to show that there was creativity, collaboration and good feelings even though their personal growth would inevitably mean they'd have to leave the Beatles and pursue their individual talents and interests.
Don't take Peter Jackson's work as cinema verite. It is deliberate storytelling that uses shorthand and editing and forced perspective to create and sustain this narrative. Many sequences are created with pieces taken from different times during a day, or even from different days and presented as though they were moments happening in the same space of time. Other scenes are presented out of chronological order. Some of that is the limitation of the available footage, but it in every sense is being used to create a narrative that is positive and dramatic, and one that is designed to push against the negativity that the original film left us with. And it was successful in accomplishing that goal.