Recent documents confirm that usually different governments were using improvised dumps, water or soil based, until the situation started to be unsustainable. Furthermore, when the state reaches that level it might be necessary to fight with a great problem, assigning a greater quantity of resources that if it had been done properly from the beginning.
Sending the waste to a natural zone, produces a considerable degree of toxicity for several reasons. The substrate filters substances, the water dissolves chemical elements and by evaporation the atmosphere receives a percentage; in general it causes more pollution that enters the system one way or another also considering other living entities. Nearby zones suffer from long contamination, and sooner or later that finite area needs to be cleaned because otherwise is a constant source of toxicity that affects everyone.
An evolved civilization should understand a simple rule when there's continuous creation of waste. If the waste doesn't enter in a closed cycle ensuring that nor a single material escapes from it, it will inexorably appear accumulation. Days are succeeded by decades, or say millenniums if you prefer. When the society reaches an epoch like the present one, with industrial processes, machines and a high rate of production and consumption due to the increased population, the disaster is ensured if none develops solid policies and sophisticated mechanisms for waste treatment. Citizens must ask for them actually.
Saying disaster implies worse quality of life, and not simply in terms of the economic idea. Quality of the air, water and aliments and with it, the number of toxins entering the organism causing health issues. Some of them critical, some bearable. And after it, the road to extinction. When species as extended as humanity, if they are irrational enough for digging a pit (some would say a tomb) without exit, the diversity could be forced to the interior causing a massive destruction of theoretically irreplaceable elements. A heritage that doesn't have known owner, but multiple responsible and of course this planet has proofs of a superior engineer. So the creatures would lose the possibility of interacting with it, after thinking without sense, putting lucrative interests like commodity or convenience first and destroying their own habitat.
This doesn't come cheap for the reputation of our species as rational beings. Never ever forget the importance of waste treatment and the responsibility about consumption. Newer generations are going to experience multiple problems just because the current global state and its inertial manners, and they aren't guilty.