Yeah, the characters are very weak and the attempts at building their backstories are clumsy and hamfisted. They are too one-dimensional, so whatever about their past you are meant to care about just isn't very interesting because the characters are so uninteresting.
The Scooby Gang flying to each McGuffin of the week is also poorly done, and wrapped up too cleanly too easily. They just seem like a bunch of amateurs getting lucky each time, not a crack team. The pilot episode didn't even establish what they were needed for, or especially why them. Skye being invited in just because set it up from the start as very unbelievable and her character annoying in a 'why are you there!' way. It's been badly written from the start.
There is just no weight to anything, and presumedly can't be or S.H.I.E.L.D. proper would be dealing with it. Leaving a very flawed, and dated, concept that they expected to coast along because er, Marvel I guess. Nothing they say about the show gives much hope they know what is wrong with it or what to do with it.
