Category pages are your money pages
Category pages target high-volume head terms ('men's running shoes'). Each needs 200+ words of unique intro copy above the product grid, a clear H1, and internal links from the home page and main nav.
Product pages need Product schema
Every product page should include Product, Offer, AggregateRating, and Review schema. Validate with Rich Results Test. Missing schema means no rich result, no merchant listing, and far lower CTR.
Faceted nav: canonicalize aggressively
Combinations of filters (color + size + brand) can generate millions of URLs. Pick a handful of high-intent combinations to index; canonicalize the rest to the parent category.
Out-of-stock products: keep the page
Don't 404 a product page when stock runs out — you lose all the backlinks and rankings. Keep the URL live, show 'Back in stock' email signup, and link to similar in-stock items.