Attacks are still possible, but if we look at xz backdoor attack[1] it was insanely complicated attack and it still failed. Its fail doesn't look promising, attack could succeed just the attacker was unlucky. Still it shows that the success is not guaranteed.
Theoretically npm can be improved in this way, if there were a separate "distro" for packaged, with dedicated maintainers for packages, who don't write code, just pull it from a mainstream and review it. It is not being done because of tragedy of commons, not because it is impossible.
Maybe I have not enough fantasy and/or creativity, but trying to imagine it, I see just a bit more of oversight built into protocols of approving changes to repositories. I mean, it doesn't seem that improved security needs an approach "destroy everything and build it from scratch", some additions on top of existing structures would do. Am I wrong?
Are you arguing that the system may be more resilient than it seems? Like, maybe there is a conspiracy working on security. And they keep themselves secret so attackers would be susceptible to under-appreciate the real level of security and make mistakes that inevitable would caught?
It seems like a over-stretched explanation, doesn't it. Care to explain yourself?