Linked and unlinked mentions do different jobs.
A backlink is page-level machinery: it passes PageRank to a specific URL, contributes anchor text, and gives crawlers a path. Its effect concentrates on the target page and, secondarily, the domain. An unlinked mention works at the entity level. It associates your brand name with topics, places, and people in text that search engines and language models both read.
Neither substitutes for the other. A site with mentions but few links struggles to rank specific pages. A site with links but no wider mention footprint looks less like a real brand, and increasingly that costs visibility in AI search, where systems quote entities they recognize.