Op can't avoid this problem if following the reviews-masquerading-as-affiliate-marketing pattern.
What's needed is to turn it all upside down: rather than reviewing new products, review broken products.
Make a site about how things break -- review broken and worn-out products to teach how to identify cheap products (where are the stress points, what manufacturing techniques exist to alleviate those). Then compare those with used products well past their warranty period that haven't broken, and look at why they haven't.
Repairability also comes to mind. Everything breaks eventually -- can't cheat entropy -- but when it does, can you easily repair it? Right-to-repair movement would get in on the action.