You are right. I provide advice and counsel in my job, and quite often the truthful answer to a question posed to me is along the lines of "I don't know and cannot know. All I can give you is an educated guess."
This is often enormously frustrating for my clients, and some of them grow angry with me because of it. No offense, but as a category I find that it is my engineer clients who often find such a response unacceptable. Many of them seem to have a compulsive need to have some degree of certainty. In fact, this often gets asked as "What are my chances [of success]?"
The truth is that in law, which is what I do, much of the professional advice is guesswork. Clients often want guarantees. Sorry, but I can't do those. Neither can I assess a set of odds as to anyone's chances to any mathematical degree. I can give my subjective, gut-level opinion, but that's all it is.
I know a colleague who always answers the chances question with "50-50. You could win, or you could lose." I think that's a little cynical and dismissive, but he's got a point.
AS