Our architecture article already answers this: the optimisation score is Google's metric, not a commercial one. Keep it healthy, but do not let it set the strategy.
If you chase the score, you end up applying recommendations that ignore MAP, margins and what the feed actually says. Google's recommendations are not malicious, just generic. Your commercial model comes first, and platform defaults come after it.
The same page also says where to look instead. You find a SKU that spends and never sells through product-level reporting and listing groups, in Merchant Center and in Google Ads, not through a weekly look at the optimisation score.
Bids are only touched once that groundwork is done. The Refine step described there audits campaign structure, feed quality, tracking integrity and negative architecture before any bid changes. On a multi-brand catalogue, that covers MAP conflicts, brand-tier segmentation and products that spend but never sell. Then comes Test, where the data decides, not opinions and not vanity scores.
We do not publish a target score. For the longer version, read Why Brand Resellers Need a Different Google Ads Architecture.