The correct response to comments is “thank you”. Or maybe, “that’s a good point.” Even if it’s not your job to change the system, or if it’s not your fault that things haven’t worked out as expected, both of these answers are valid and useful.
Feedback is a gift. It lets you know precisely what the other person wants or needs. After receiving the gift, it is up to you to accept it or not. But closing comments with an argument or by looking ungrateful makes it less likely to be offered to you again. And if you receive feedback from a customer or prospect, if you shut them down, chances are they’ll walk away and get their attention and trust elsewhere.
When you say “no problem” you are letting go of yourself, refusing to acknowledge what has been said and closing the door to useful interaction. Because there is a problem. Exploring what the problem is is much better than denying it.