That is an entirely subjective opinion on this and one I don't share. I think there's great value in this archaeological dig. This is the way we find rare items and evidence of the past that has often been lost to time. Just because this isn't Carthage or some other ancient site doesn't mean there is no value here.
Also, if you take issue with the neglect and destruction of other buildings (something I do agree is unfortunate), shitting on the work being done here isn't going to help. If anything, it only contributes to a sense that Toronto has no history worth saving or preserving. If you want adequate historical preservation, there needs to be an element of "all or nothing." Otherwise historical preservation comes down to endless, subjective debates that leave everyone unhappy.