>Ideally, Google wouldn't credit one part of the site that is lower quality than the other part. //
Site authority presumably wouldn't be a thing if it didn't produce good results. Sites that allow crappy content will tend to have more crappy content and so a page on such a site is less likely to be what someone is searching for; as long as that stands then site authority will still be useful and shouldn't - IMO - be discounted completely.
Site authority presumably wouldn't be a thing if it didn't produce good results. Sites that allow crappy content will tend to have more crappy content and so a page on such a site is less likely to be what someone is searching for; as long as that stands then site authority will still be useful and shouldn't - IMO - be discounted completely.