Over 5,000 pages in Google Search Console are not indexed and are leading to 404 errors. Would fixing these issues improve SEO?

We use Shopify, and as per the title, I noticed we have over 5000 pages that are not indexed by Google. Some of them are for products that we had and have since sold out. Would adding redirects to these links which lead to the main collections help in terms of SEO? Or would our time be better spent on creating quality blog content?