I don't really agree with this. Characters like Luke Cage, Daredevil, and Iron Fist are not even on the radar for a feature film. We have a schedule of films that go through 2015 and others heavily talked about (Dr. Strange, Ms. Marvel, Black Panther) along with sequels (Cap3, Thor3, GOTG2) that most likely fills up the schedule through 2018. If they want some of these other characters in live action, SHIELD is the perfect place to introduce them.
Cage and Iron Fist were definitely on track for feature films several years ago, and even had leads and directors and scripts attached. That was before the whole Avenger MCU thing, of course. And Daredevil is definitely still feature film material.
As I've said many times before, Marvel Studios is kind of in a predicament with their "street level"/Marvel Knights heroes. Feige has hinted in recent convos that he doesn't see them as blockbuster movie material in the league of what they're planning now; but it would be an absolute waste to let these characters gather dust on the shelves.
I still think the best strategy for Marvel is to create a smaller "Searchlight" studio to handle the Marvel Knights-level characters. When Avi was running things a few years ago, he said that the studio's strategy was to produce two blockbuster films per year with budgets around 150 million, and one smaller film budgeted at 30 million. They've obviously dropped the second part of that strategy, but it might be time to re-examine that.
And I agree that television would be a great medium for these types of characters --- the shows could be produced pretty much on the cheap. And Marvel Television originally had plans for a *lot* of shows in development, including Del Toro's Hulk; but all those turned into vaporware except for SHIELD.
SHIELD is still a gamble. They've got past the first hurdles, but the biggest hurdle still remains: gaining an audience and becoming successful. We all hope it happens, obviously; but if it doesn't, you don't want to be stuck throwing a bunch of A- and B-list names under the bus, essentially.
Luke Cage, Daredevil, Iron Fist, Punisher and company relegated to guest starring roles on an unproven network TV show? Far too big a gamble to take. They belong on film, or at least headlining their own shows.