Every channel that displays your products needs a feed in its required schema. Google Merchant Center has its own format; Meta has its own; Amazon, Walmart, and TikTok Shop each have theirs. Mature ecommerce platforms either generate these directly or via integrations.
The most-common feed problems are attribute mismatches (missing GTIN, wrong category, low-quality images), policy violations (restricted product categories, prohibited claims in titles), and stale data (the feed shows in-stock but the product sold out an hour ago). Each one suppresses your listings without an obvious warning.
Feed quality directly affects paid acquisition performance. A clean, optimised Google Shopping feed will outperform an unoptimised one at the same spend — sometimes by 2–3×. Title structure, image quality, GTIN coverage, and category accuracy each independently influence ranking inside the shopping carousel.