IMO it's not worth the hassle to add user feedback, because A) it takes a lot of work from the website admin B) it's usually extremely low (maybe negative) value.
A friend of mine who frequents recipe sites pointed out to me once how often the comments are some variation of "I made this except I didn't have any X, Y, or Z so I used M, N, and O", which is great for them but it doesn't really tell you if the recipe, as written, is any good.
I suspect the recipe sites care about comments and other user-generate stuff because that's how they track "engagement" and collect data to feed into their SEO/ad targeting/sales pipeline.
Yes, unless the recipe called for sugar and the "chef" who tried it was clueless and subbed something dumb like sweet curry powder and then complained the recipe sucked.