It's just that people give the movies subjective significance instead of judging it purely on story. The reason Iron Man is so high always is because it was the first movie, Avengers because it's the first team-up movie that connected a universe of 4 different franchises, Panther because it had a powerful political statement that's gonna change diversity representation from here on forward, Infinity war, while still being one of the best story wise, gets a lot of points because of everything that was accomplished before it. Ever Guardians of the Galaxy gets a lot of pity points for being the first movie that had the balls to change up the genre. Sure if none of these happened the movies would look a lot different today, but if you're gonna make a ranking based on pure story those things shouldn't be factors