Diagnose it properly before you fix anything
Open Search Console and compare the last three months to the same period last year. Split by query type. If impressions are stable or up and clicks are down, you are losing clicks to on-SERP answers. If impressions themselves collapsed, that is a ranking or indexing problem and a completely different fix.
Segment by intent too. Informational queries have been hit hardest. Commercial and transactional queries still send clicks, because people buying want to see the shop.
If it is click loss
Shift effort towards queries that still convert. Comparison pages, pricing pages, and anything where a person needs to see the actual product survive better than definitional content.
Then make peace with being cited rather than clicked on the informational side, and start measuring mentions and citations as an outcome in their own right.
If it is a genuine ranking drop
Look for the usual causes before blaming an update. Check for lost links, a migration that broke redirects, a template change that stripped internal links, or thin pages that got deindexed. Compare your losing pages against whoever replaced you and look for what they have that you do not.