For nearly half a century, LOTR was considered unfilmable due to the depth and breadth of the material.
Film is a VERY different medium, and there were always going to be compromises.
Jackson, and the people he worked with were actual fans of the works, and tried to retain as much as they could. But, in the end, some things didn't translate well into film. And you can't ask someone to sit for 6 hours in a movie theater (especially not with the "Bladder Assassinator" size drinks). Nor can you ask theater owners to take a massive haircut due to what such films would do to their per-theater revenues.
Jackson & Co walked right up to that line, toed the line a few times, played around with jumping over, and made as few cuts and changes as they possibly could to still deliver the films on-point.
And most of the cuts were things that simply didn't move the plot forward and were just "Oh and this happens", with no actual payoff.
What we're looking at with the Amazon series is the equivalent of handing it over to JJ Abrams.
"Cut out all the dialog! We need 300% more lens flare!"
It's the difference between having a skin tag removed and having your entire epidermis flayed off.