A non-percentage-based one would be more interesting. The whole MCU phenomenon would likely increase the absolute number, but I doubt that it would be as dramatic. What the chart as-is fails to show is the specific loss of other types of movies that have moved to other media.

Ever since made-for-cable TV series went mainstream with HBO in the late-90s, a huge chunk of yesterday's non-blockbuster movies have become today's TV series. And there are massively more TV series than ever before.

That "25%" in the 80s shows you that there were already tons of those, and it's easy to remember them (Jaws 2, Empire Strikes Back, Temple of Doom, Aliens, Godfather Pt 2, etc etc etc).