The way I read the support article, Firefox should offer to show this feature on Amazon, BestBuy or Walmart:

Shop online with more confidence using Firefox Review Checker

On those sites, there's an extra icon (looks like a price tag) in the address bar near the star button used to bookmark the current page. Do you see that on yours?

I'm running into the same problem. None of the above-referenced retailer websites features a price tag icon in the navigation bar when visiting a product page.

I'm running FF 133.0 (64-bit) with Ghostery, PrivacyBadger, and uBlock Origin installed as extensions.

Could you check the preference mentioned in another thread to see whether it makes any difference for you? Here's how:

(1) In a new tab, type or paste about:config in the address bar and press Enter/Return. Click the button accepting the risk.

More info on about:config: Configuration Editor for Firefox. The moderators would like us to remind you that changes made through this back door aren't fully supported and aren't guaranteed to continue working in the future.

(2) In the search box in the page, type or paste shopping and pause while the list is filtered. Firefox should list a dozen-plus rows.

(3) If the browser.shopping.experience2023.enabled preference is set to false, try double-clicking it (or clicking the toggle button toward the end of the row) to switch the value to true and see whether that makes any difference

Ref. https://support.mozilla.org/en-US/questions/1476784#answer-1691425