which is the title of an interesting article by Grant Brisbee on SBNation. He took two games from different periods that had very similar stats and was able to look at video replay of both.
Apr 13, 1984, Mets--2 at Cubs--11, 270 pitches, 27 baserunners, 74 plate appearances, 1 mid-inning pitching change
Apr 17, 2014, Brewers--2, Pirates--11, 268 pitches, 27 baserunners, 75 plate appearances, 1 mid-inning pitching change
The 1984 game lasted 2 hours 31 minutes
The 2014 game lasted 3 hours six minutes
Brisbee did an inning-by-inning breakdown of stats and included comments by announcers and commercials and then discussed what he saw as differences contributing to the 35 minutes of extra time.
http://www.sbnation.com/a/mlb-2017-season-preview/game-length
Apr 13, 1984, Mets--2 at Cubs--11, 270 pitches, 27 baserunners, 74 plate appearances, 1 mid-inning pitching change
Apr 17, 2014, Brewers--2, Pirates--11, 268 pitches, 27 baserunners, 75 plate appearances, 1 mid-inning pitching change
The 1984 game lasted 2 hours 31 minutes
The 2014 game lasted 3 hours six minutes
Brisbee did an inning-by-inning breakdown of stats and included comments by announcers and commercials and then discussed what he saw as differences contributing to the 35 minutes of extra time.
http://www.sbnation.com/a/mlb-2017-season-preview/game-length