Can over-optimized anchor text from a previous SEO still suppress rankings in 2026?

Looking for some input on a specific situation. We have a key landing page on a client's site that used to rank well for its main keyword, but has been steadily dropping since around August 2025 and hasn't recovered since (except brief spurts). A competitor with a lower Domain Rating and far fewer backlinks is consistently outranking it. After digging into the backlink profile, I found what I think is the culprit: the previous SEO specialist built