Other shows are cheaper to produce and so can make a profit more easily. It comes down to price per show here. This is an expensive show to produce. And if the ratings are not high then advertisers won't pay for commercial space. This will then mean that the cost is too high for moneys received. And so it will mean cancellation.

Being picked up for the back 9 episodes is a good sign. But I have to say, I was not thrilled with the actual characters on the show. Some are just annoying - like the two children scientists. Some are underused like Ming-Na (who I really like, especially when she was on Stargate Universe). I thought the writing was relatively good, but so far I didn't like the people aside from Coulson. And so I stopped watching in the middle of the third episode.