Dismissal is not constructive criticism. There's a sizable difference between "meh, nothing to see here" (which is the original comment in this thread) and "here's how this could be better".
Ruling out a product and dismissing it based on projected ROI is not criticism. That would be called "making a business decision," not providing constructive feedback.
If the product does not provide a decent ROI then you are right to dismiss it.