Not every plot element is a spoiler.
True, but determining which are spoilers is very subjective, and those that are spoilers will be mixed up with those that aren't in any well written summary. Yes, you could put a spoiler warning half way through the summary allowing people to just read the beginning and not spoil the ending, but what really is the point? How many people are likely to want to know the beginning of the plot and not the end? (And people trying to decide if they want to watch the film don't count - they are looking for a blurb, not the first half of a plot summary, they serve very different purposes.)