Category pages written to be landed on
The highest-value pages in any store and usually an H1 with a grid under it. They need the copy that answers how to choose, which is what the searcher is actually asking, placed where it does not push the products below the fold.
Product pages that are not the supplier feed
If your description is the manufacturer text, so is everybody else’s, and Google picks the store it already trusts. Rewriting the top sellers is a finite job with a measurable return; rewriting all forty thousand is not, and nobody should pretend otherwise.
Faceted navigation brought under control
Colour times size times brand times price is combinatorial, and left open it produces more URLs than you have products. Decided per facet: indexed where people search it, crawlable but not indexed where they do not, blocked where it is noise.
Out of stock and discontinued handled deliberately
A product that sold out should not 404. It should stay, say so, and offer the replacement, which keeps the links and the ranking for when it returns. Discontinued lines redirect to the closest live equivalent rather than to the home page.
Structured data that earns the extra pixels
Product, offer, availability, price, review, and the breadcrumbs. Correct markup is what puts the stars and the price in the result, which moves click-through more than a position does.
Speed on the pages that carry the money
Measured on a category page on a phone, not on the home page on a desktop, because that is where the visitors and the abandonment are.