Eh, there may be 12,000 names on the list, but that doesn't mean you have to wait for all of them to get a garden before it's your turn. Many of those people will have changed their minds in the meantime, or they don't like a particular lot that's freed up, because you usually can't just leave it as-is. The one in the article burned down, many other lots have houses that violate new regulations but were grandfathered in, so you have to demolish and rebuild. Then there's the workload of actually gardening...

I'm also not sure where they're getting the 12,000 from, since to my knowledge every "colony" manages their own waiting lists. If they're just adding the number of people on each list to arrive at the total, they're double-counting people who're not looking for a garden in a particular location and appear on multiple lists.

All in all, if you really want a garden, it's absolutely feasible with a few years of waiting. And if you just want to dream about having one, you can still put your name on the waiting list and politely decline each lot they offer.

EDIT: there's also a sharing platform for people who need help gardening and those who want to do it: https://www.datschlandia.de/ That is another way to get the benefits of a garden bypassing the waiting lists.