Otherwise, a lot of people will get that USE flag disabled (as it's not enabled by default) and they would need to read metadata.xml to see they need to enable it. Showing and ewarn if old drivers are installed would help Thanks Reproducible: Always
I think any such logic should be part of nvidia-drivers, not cairo. Maybe even an explicit dependency, like "!x11-libs/cairo[-legacy-drivers(-)]". Therefore I propose WONTFIX for this bug.
I agree that a dep in affected nvidia-drivers versions would be interesting
this flag doesn't even exist anymore yes nvidia-drivers builds fine.