Why isn't Lordship Lane having the same problem?
There are shops competing with each other. Many residents of ED are now coming to the market on Saturdays, yet those shops still make money during the week! The same is for towns like Penge and Sydenham. (one FM in Penge and another in Crystal Palace). No one resents farmer markets. There are so many in London now that you just have to pick and choose. So if the one at the Horniman goes, people wanting to eat good food, good vegetables, as they used to be before the advent of Sainsbury and Tesco, go somewhere else. People who buy seasonal organic vegetables from internet companies, like Riverford, will continue to do so for the convenience and the quality.
Hasn't internet changed our way of shopping? So where is the problem? Why don't DR shops producing nice things, have a stall up at the Horniman? If that is the place to be seen, that's is where you have to be, even for few hours.

I was told that DR was a nice shopping area in the 50's and 60's. Who is the Enemy Number one, the Farmer Markets or the Big Supermarkets which have cut off trade in the area?

The farmers bring only what they produce/make on their land.
They also got expenses to think about, like transporting goods from one market to another, labour costs, stock and land. The organic vegetables stalls pay over £8,000 per year to have the land certified as organic. If they sold all their produce to supermarkets like Sainsbury, Tesco, Asda, etc..etc... for peanuts, they could not survive. Only by doing markets like that, they can now make a reasonable living.
I hope the market will continue in the New Year, become more interesting with new stalls and produces, so we all benefits, especially our children.