This seems analogous to how we tackle email spam and general malware. It means that there is almost always a target valuable enough for bad actors to continue trying. However, unlike email (mostly...), package managers are centralised authorities (and anything out-of-band is surely the developers problem?).
My ill-informed feeling is that we might need to change the culture of lazy versioning with rapid releases and focus on stable, deeply scanned versions at registries. There will be some effect of volume and scale so I could be off, but it still seems telling that this impacts high-churn languages more often.
I don't know, I would love a comprehensive article that explores the landscape right now.