No, its still a very useful mitigation tool.

1) Package owners will often realise they've been hacked quickly, since there are releases they never authorised. This gives them plenty of time to raise the alarm and yank the packages

2. Independent security researchers and other automated vulnerability scans will still be checking the latest releases even if users aren't using them

Yes it's not a perfect defense but it would help a lot.

Some people would set up tooling to look for compromises the moment they get published. What's neat about this is that as an attacker you have no way to determine beforehand whether you'll get caught by this. So you would run your attack, it would lead to a compromised package being published, then the world would get a chance to look at it and see if they can detect the issue with it. This would of course lead to attackers being a lot sneakier. But I think due to the opaque nature of what checks people are running against packages and what they might notice, a much smaller number of attacks would make it through. Of course the ones that did by definition would be the ones that were impossible to detect and would thus stick around a lot longer.

These malicious packages are being caught by the authors, and by automated package security scanners, not just by end users. npm should start setting this 7 day cooldown as default.

Mine's set to 1 day (seems to be enough from all the cases we've learned about), I got you.

Also seems like this attack and most others were caught by automated tooling from 3rd parties