I think the system could be simplified even more user-wise. But it would take an additional workforce provided by a third party, therefore a working business model to maintain the process should be figured out.
The people who are willing to give stuff away usually don't want to bother about photographing their give-away items, uploading pictures and even sorting the items properly, it would be best for them if they could just pack all the stuff which they don't want to throw to the rubbish but don't want to keep as well and call someone to pick it up. I think those who have a lot of such items and want to get rid of them would even pay a few euros/dollars for someone to do it.
There could be a dedicated service for this. All the things collected from people like that would be brought to a warehouse where they would be properly sorted, evaluated and then some of them could be either sold for a low price, given to second-hand shops or for free to people, etc.
I initially thought of a website where the items sorted and photographed in the warehouse would be uploaded and people willing to get second-hand items for free or a low price could search what they need and order a delivery to their home, but I'm not sure if and how this would cover the efforts of the third party, the items should either cost some money or/and the platform should have a subscription fee, etc. The delivery could have a separate fee, it would be like second-hand shopping online, some items could be free, some not.