At a previous job, a significant percentage of the feedback we received was about the feedback prompt itself. Users just want to get what they came for and then leave the site. They rarely do anything that doesn't directly benefit them, unless they're really happy, or really angry. For everything else, there's analytics.

Analytics answer questions like "is this content worth translating", "is that element a good use of screen real estate", "is this browser worth supporting", "how do people find this page (and what are they looking for)". You can't get that out of a feedback form.

> which is not vital

Not every website is run as a charity.