This piece includes spoilers for “Avengers: Endgame.” When the first Marvel Cinematic Universe movie, “Iron Man,” was released, George W. Bush was president, Miley Cyrus was Hannah Montana and...

Right now, you’re probably wriggling in your desk, breathily whisper-chanting “summer” as a gigantic clock ticks down the minutes until school’s finally out and you can break into a deceptively...