Make become a seller a bit more difficult with some skin in the game ($2,500 deposit if you sell more than 15 items per year? In person identity verification?). Sellers used to meet with buyers agents (cost money and added identities).
Caught selling garbage (product marked new actually used, totaly fake junk) enough times -> gone from marketplace and hard to get back in.
The reality is Amazon doesn't care - there IS a market opportunity here for someone to take them on with trusted product catalog and quick shipping (using UPS / Fedex). I wish somebody would straight compete with them rather than all the complaining to politicians.