Interstellar is not an action movie. It's an epic, so I would say the near-three hour runtime is justified. Same goes for LOTR.
You could probably argue that Avatar didn't need to be so long, but it's James Cameron and he can do what he wants and it didn't stop the film from making money. Anyway, that's kind of an epic too, with an action movie climax.
Nolan does tend to run a little long, but besides TDKR and Interstellar none of his pics run longer than two and a half hours and he balances story and action pretty well with much more of the former than typical blockbusters, so I think he gets a pass.
The two Avengers movies have so much going on that the long runtimes are pretty justified.
The main perpetrator seems to Michael Bay, I think. The problem is his movies keep making money, so the studios don't feel the need to force cuts.
He's not the only one who embellishes, of course. It just the times, I think. People are willing to watch longer action movies now, so we see longer action movies. Pacing is much more important than length, and quality too, as Silverwook points out.
I'm a big supporter of the 90 minute film, but I'm also a big supporter of the two hour plus film. If that's what the filmmaker needs, so be it. Better than the studios getting in the way, as has happened far too often in the past.