Actually, it does work well! In my local Buy Nothing group, and I assume in others as well, people just leave stuff out on their porch at the arranged time, so that no physical contact is made except through the item. In that sense it's no more or less risky than delivery services or curbside pick-up at stores.

I'm wondering what impact COVID might have on this.

On the one hand, some people have reduced income during the pandemic, so they don't buy less brand-new first-hand stuff.

On the other hand, some people might become more wary of second-hand items as disease vector.