I think it's important to be clear about "addictive" because people use it in different ways. If by "addictive" you mean "really compelling" then, sure, it may not be intrinsically terrible. A product that, for example, makes it really compelling for users to improve their physical health or fight climate is probably not terrible.
But the clinical definition of "addiction" which is why "addiction" has a strong negative connotation is that for something that is so compelling that your need to use it causes significant disruption to your quality of life of that of those around you.
Read the testimony again. The argument here is not just that Facebook is super engaging. It's that Facebook use harms its users and the world at large and its level of engagement magnifies that.