Have you misread the decision?
This is not what it says at all?
Even if you only read the summary on here, it's clear: "the ECJ has said that marketplaces are not responsible for infringement when all they do is allow third parties to display infringing goods for sale on their site."
Your carboot analogy stands - the organiser would not be liable.
If, however, the carboot organiser put up signs saying "buying fake [Chanel] handbags here", it's more likely that they are doing something wrong - and that's the view of the court here, too.
This is nothing new - it's been around since 2000, when the eCommerce directive was passed. If a provider is not aware of an infringement, or circumstances from which an infringement would be apparent, it cannot be found liable. If, once aware, it fails to take action, it can be found liable - it loses it shield. There is no obligation on an ISP to inspect every bit of tat - but, if it does, it needs to ensure it inspects well, to mimise risk.