I guess he's referring to the length of a single episode but, in a world of streaming, that seems a little arbitrary. At home, nothing keeping you from pausing a film halfway and picking up the next day just like a TV series. Obviously telling a single story in 90-180 minutes is a different form from telling a storing over multiple seasons of 30-90 minute episodes in different from a miniseries or single-season series. But they're all just artistic (and financial) choices.

While there's arguably been an overall shift to shorter content, I don't really see a marked falloff in movies being produced.