Many years ago I pointed several people to Etsy and Not on The Highstreet. Both platforms were started by people with a background in marketing. I was one of the first Traders on Not on The Highstreet. They sold it to me that they really were looking for products that were unique and not available on every high street. Initially we did really well but then just about every indi high street retailer had a shop on there, all selling similar products to one another. Then they allowed anyone to join! The only ones that really gained were the owners (google not on the high street history).
Both NOTHS and Etsy and now so flooded you might as well be a grain in the sand.
If you have a good, well known brand or unique product you might be able to top up your income slightly.
It's a bit like, craft, antique fairs, farmers markets, the only winners are the organisers because for every small indi that falls off, there's always someone else that's desperate and willing to give it a try.