Replace marketplace with platform, anyone who calls themselves a platform and competes on the “kill all competitors” level should be regulated as common carrier/public space.
There are numerous ways to identify platforms vs marketplaces and not all of them are related to total market penetration. But I think the legislation should look in that direction, give the FTC the power to declare a company a platform in its space and then allow it to regulate that company in the same way utilities are regulated but obv updated for the internet age.
I think the biggest hinderance to this sorta thing is that all law makers are increasingly biased and refuse to acknowledge their favor. They pretend instead that they are in fact impartial and any appearance to the contrary is simply necessary due to the importance of the issue at hand, or the extremists involved (“I’m really a centrist, they’re just nazis, so I appear to be far left” and vice versa).
Last time I needed one, I was unable to buy an effective bandage wrap in person, I had to order online. My local Walgreens only had their own house brand "self stick" type that doesn't really stick at all.
Went to buy some wrist braces, again, only their house brand. Many styles of wrist braces exist, they sold one type, the type I didn't want.
For some house brands, such as Costco, they provide a huge competitive force in the marketplace. An example is Costco Diapers, which are rated really well, and basically establish a price at which other "name brands" have to complete. There is a possibility that they are creating a downwards pressure on the price of diapers overall. (Or that they are colluding to ensure prices don't fall too far, huh, never thought of that angle before!)
My local grocery store's brand is generally untrustworthy. I hate it when they are the only option for buying something. The 3 times I have tried their yogurt coated pretzels I have gotten an upset stomach, and I normally have an iron stomach that allows me to eat street food around the world with aplomb.
Funny enough their house brand "sweetened flavored sparking water" is really my preferred brand, so they get it right some of the time.
But from one perspective, isn't this argument hypocritical of us? If I go to a baker, I kinda expect everything in the bakery to be "store brand", and in fact many bakeries been scandalized for not selling their own goods! Heck if I go to my local farmer's market I expect what the farmer sells what they grew, and again if they are just reselling produce, social media scandal!
This entire idea of stores being a "marketplace" for multiple brands is only a recent aberration.
So maybe what are seeing is just things are just slowly returning to a world where everything is "store branded".