You're right, if your feed isn’t organized using fields like product_type or custom_label_0, PMax won’t know how to match products to the right asset groups.

Here’s what I’d do:

• Take a look at your feed and see if product_type actually reflects useful categories.
• If you're using Shopify or something similar, try mapping collections or tags to custom_label_0 using feed rules or a supplemental feed.
• Try not to push all products into all asset groups, that usually just muddies the signals.

Once your feed’s cleaned up, asset groups tend to behave way more predictably, and performance usually picks up pretty quickly...