Any statement you make about the world or anything in it will be "just" a theory at best - a working theory that agrees with observation if you're lucky. I don't know why people always keep picking on the word "theory"...?
Just because we don't understand how something is done does not mean it cannot be done. I feel that first I need to understand someone's work before I can criticise, let alone dismiss it. I don't think we can take anything away from people like Brian Schmidt just because we cannot fully (or hardly at all) understand their work. But it is much easier to dismiss than to make the effort (probably a lot of effort!) to understand.