Whedon, Tancharoen and Loeb are essentially blaming the audience for the show's shortcomings. It has been poorly paced and the characters have been underdeveloped, but somehow viewers who have been dissatisfied are at fault for not having patience. It is possible to lay the foundation for a series with stories that are well-written, exciting and feature good character development. Agents of SHIELD just hasn't delivered.
Some of what they said contradicted things they said in earlier interviews. When the show first started, the producers claimed that they structured the first 13 episodes so that they would tell a complete story, just in case the show did not get picked up for a full season. Now they are asserting that the first 12 episodes were just the setup for the series, "the first hour of the movie," as Loeb put it. (Clark Gregg likened the first half of the season to having to eat dinner before getting to dessert.) If Loeb has ever watched a Marvel film he knows that the first hour is never a muddled slog, even in origin stories. The beginning where the plotting and characterization has to be crisp to grab and keep attention. Maybe the writers can deliver that in the back half of the season.