What do you think about creating a demand-based portal - as opposed to all the supply-based ones like Allegro, Aliexpress, etc.?

We have an endless number of portals on the market that gather sales offers. The person searching through these ads is someone wanting to buy something. What if we were to reverse this? What if the ads were posted by people who want to buy something? In a way, it would be an exchange of supply and demand. Why am I pondering on this? It mainly concerns unnecessary and used items. Almost everyone has them at home, but most people don't want to post an offer and wait for a buyer. It's a barrier for most. They prefer to throw things away or keep them in the attic or basement for years. If the portal gathered purchase offers, people with unnecessary items would have a smaller barrier to overcome because the buyer would already be there.