Dogs were not originally seen as pets in these countries, but rather as work animals. If you were to visit rural areas in an Eastern European country 5-10 years ago, you'd find that people that owned a dog had them chained up next to their fences, used them for protecting their livestock, or used them for hunting. If one were to escape, the village would have an extra litter of puppies that would most likely be dumped in the middle of a field or another village.

I'm not arguing for horror stories like puppy mills, which I am completely against and agree with you in those kinds of cases. But countries like Romania, Bulgaria, Greece, etc. are a bit different. Most of these dogs come from rural areas, which managed to live off of garbage until now.

The alternative to the shelter is euthanasia, but I am honestly glad if a responsible person decides to adopt the animal instead. What you should really be against is people paying to adopt a specific breed from a breeder, not those that free up space in actual shelters.