Isn’t that the current status quo?

The GDPR has over 100k words, and those words are certainly less than 0.01% of the thought that has gone into this problem.

Agile laws might not be so terrible.

Counteropinion: agile laws would be absolutely terrible. Either people wouldn't take them seriously because they're going to change in a few minutes anyway, or people would take them seriously and be bound by law by the equivalent of late-night untested code that seemed like it should work.

Charitable interpretation of their comment: Law is implemented and then rapidly improved upon.

But yes, I think your take is more realistic as any measure that allows rapid changes also allows willful politics to rapidly make a mess.

Imagine being charged for something that you didn't yet know was a crime because you didn't watch the morning news.