The parent was suggesting to regulate first and fix broken regulations later. That's almost literally moving fast and breaking things.
The assumption is that introducing a bill to regulate dark patterns is the same as "moving fast". This bill hasn't even made it to committee [1] and darkpatterns.org was started in 2010 [2]. I think an argument could be made that the US government is actually moving pretty slowly on this topic. GDPR has been in place for over a year, so there is significant data to understand the implications of this type of regulation.
==and fix broken regulations later.==
How is this different from a software product releasing an updated version? Microsoft Excel is on v16 and I don't think anyone is accusing that product of moving fast and breaking things. I wish we spent more time adding features and fixing bugs from past legislation.
As to your second point, I also wish we spent more time adding features and fixing bugs from past legislation. I don't think that happens nearly enough, which is a major reason I don't trust our ability to just fix shoddy regulation after the fact.
The idea people seem to be repeating is that this will be ineffective. It seems to me that GDPR provides a pretty strong framework to learn from and build off. Europe effectively launched version 1.0, so now we can implement the best parts and eliminate or improve the weakest parts. We aren't starting from scratch or searching in the dark.