I'm sure that's true of some directors. I think Jon Chu with In the Heights took as much time as he needed to tell the story he wanted to tell.
I disagree with the OP's statement that nearly every movie today is 20 -- 30 minutes too long and that directors should keep the running time under 2 hours. IMO that's an overly broad and absurd comment. Every film is different. Movies (and plays) are not like TV programs, which have to fit designated time slots.