The general plot to Avengers: Endgame leaked before the movie was released and it was both dismissed as being too ridiculous to be true, while others felt that if the leaks were true it would be a terrible movie. The leaks did turn out to be pretty accurate overall. yet now Endgame is considered one of the best films in the MCU. I think most films would/could sound pretty boring and/or strange when all you have are simple scene summaries without any of the dialogue, performances, music, cinematography, etc. to make them engaging. Plus, the people who leaks movie plots don’t usually have the full scripts at hand, but have found ways to “peak” into the production, and that’s definitely bound to strip away a lot of nuances and important details.
I don’t think that’s to the credit of the film, though. What people were criticising (namely Cap’s ending) was accurate to what happened in the film.
I read the leaked Last Jedi synopsis and was very disappointed, but when I saw it executed on screen I was relieved that at least what was written was carried out to the best of the production’s ability. The operative factor on my experience, however, was that my disappointment for the plot was already out of the way, and it was only that I was braced ahead of time that my moviegoing experience wasn’t as negative as it could have been.