Like, obviously, marketplace is tied to Facebook the social network. It's how they authenticate sellers are real people and connect them to nearby people. It does a huge disservice to consumers to try to disconnect the two.
That isn't what is happening here. They are being fined for preferential treatment to their own service on their platform. That isn't the same thing as you're saying.
They're clear about the fine, but then it's all handwavy language about what a concrete violation even looks like. So it's impossible to even have an opinion because nobody even knows what we're actually talking about.
Best I could gather from the article is that this has something to do with paid ads on Facebook and Instagram that link to Marketplace vs. paid ads that link to other similar services (like eBay I'm guessing?), and that there's something extra-special about the Marketplace ads that the eBay ads don't have. But what even is the special thing? And is the article even accurate on this? Because it also refers to Marketplace listings as "ads" so it's not easy to parse.
Here it deals with the fact that in that area Meta is both a platform provider and a player in said platform, and that they take advantage of the former to hamper competitors. I can't see how it's related to what you're suggesting.
And anyway the EU never had specific legislation at the time Marketplace was introduced hence why they are having to use the EEA agreement as the basis for their actions. Which is basically a generic "do nothing bad" clause.
It then exacerbated this by imposing unfair trading conditions with a terms of service that authorised the company to use ad-related data — generated from competitors who advertise on Facebook or Instagram — to benefit Marketplace.
The reason the use EEA legislation is presumably because Iceland, Liechtenstein and Norway are EEA but not EU states, but fall under scope here.
I simply cannot even comprehend the kind of entity/mind that sees this as an issue. How does the EU even get anything done?
Think of the poor users! "Exposed" to Facebook Marketplace, oh the humanity! How evil of a company to link to their own services on their own website! We must regulate the links!
This ridiculous mentality is why the EU has strangled its tech space to death, why it has missed out on trillions from the mobile era and will miss out on trillions from the AI era, why all of your best engineers come to the US, and why the EU has completely and utterly failed in consumer facing technology.
The EU is more interested in hand wringing and manufactured moral panic than actually getting shit done. Marketplace in Facebook feeds? So what? Like, who gives a shit? The users certainly don't. It works, people like it, ship it, move on. God, what a suffocating bureaucracy.