Toy/clothing swaps?

Great question!

My kids are young adults now, so I'm past the age of handing off baby and child gear. However, I am very active in my local Buy Nothing Group and see loads of good quality gear being exchanged on a regular (daily!) basis. Not what you're looking for, but I recently outfitted a guest room with significant contributions from my group, including a like-new upholstered queen-sized bed frame. Buy Nothing Groups are hyper-local. They are all about building community through the free exchange of goods and services. Consider seeing if there is a group in your neighborhood.

I love your thoughtful post.   Reuse (at both ends, acquiring and retiring) does take a bit of effort and patience.  I am a seasoned participant at it.

What I have seen is mostly friend/family circles passing things around among themselves, and parents who post needs and offers on Freecycle, Nextdoor and Facebook, and my favorite, which is yard sales.   

My child's preschool (this was pre-covid) used to have an annual yard sale, which raised some money, but probably more beneficial, it was like a swap-meet for families and we ended up recycling a lot of things among ourselves. 

Until my kid started caring about his clothes, almost all his stuff came from yard sales, etc.  Up until at least first grade, most of his Christmas gifts also were yard sale finds that I collected in summer or fall, and squirreled away until holidays and birthday.  Many kids' items at yard sales are barely used or just take a little effort with cleanup (try dish soap + a magic eraser) and presentation (make a toy gift basket, use treat bags or attractive containers from a dollar store, and curate groups of toys like old playmobil, duplo, dolls, cars, etc into an attractive unit) 

Now as a teen, my kid & friends enjoy thrifting for wardrobe finds, which I think is so cool. 

Infant gear is a  problem area for waste, because the bay area is fairly affluent and many new moms are gifted a mountain of things for newborns.    Some techniques for new moms in this position are:  create a wish list that includes clothes in 6-24 month sizes otherwise people will give you newborn sizes only, and don't be afraid to specify diapers on a wish list.   If you receive too much clothing, either try to make a few retail exchanges for the same outfits in larger sizes, (appreciating the same thoughtful gift),  or don't snip the tags until you are about to use the item.  New-with-tags baby things that you didn't end up using are easier to donate and appreciated by charities that support moms in need, as some can accept new but not used items.  If you end up with too many diapers, these are very easy to donate (food banks and social workers need them). 

When my baby's grandma insisted she needed to buy a high chair (before my baby was sitting up or eating solids), I insisted we try a couple of yard sales first.  I just went to Craigs List Yard Sale section and searched for key word High Chair, and instantly found 3 options in my own neighborhood.   I, Grandma and the seller were all very pleased with the outcome.   Try the technique of searching for a key word in Craigslist Yard sale posts related to kids age, even if you don't need that exact thing:  Crib, duplo, baby kids, etc, to find a family yard sale that will have things for the age you need.