My response won’t help, but I am just trying to think about the barriers to effective trading.
One problem is identifying things that you DON’T want and taking the time to do something about it. You never know when you might need something. In the rare event that I have parts I am certain I won’t need AND which have substantial value, I put it on bricklink. But bricklink is very time consuming and I’d rather invest my spare time building or buying things I need rather than getting rid of things that I don’t need.