Decline of the Roman Empire

I do somewhat agree with the Monocausal Decay Theory. But, there are parts of this theory that I do not agree with. One part that I do not agree with is enviornmental degradation. This states that gradual environmental degradation caused population and economic decline, and this includes deforestation and and excessive grazing. Lead poisoning seems to be another part of the theory that I'm not too sure about as not everyone drank wine or cooked in lead-based pottery, but I do see how those who did were affected by the poisonous lead. But the part of this theory that I 100% agree with is the spread of disease. This was definitely a huge factor in the decline of the Roman Empire as diseases such as smallpox, measles, and even plague ravaged the empire. So all in all, I do agree with this theory of Monocausal Decay.