I basically agree with you but I think the main reason alcohol is considered the most dangerous is because it's so widespread. In moderation I think it's a lot better than cocaine/heroin.
In 2013 as a student my school talked to us about the dangers of marijuana, and I believed it because...the teacher told us. But a year or two later I researched it and found out it isn't as dangerous as they said, and may even be safer than alcohol. It's a shame that they still preach propaganda and demonise weed when they should instead tell students where they can buy it for a good price /s
Well, here's a thing, the purpose of these charts are to represent the dangers that each drug has on an individual and the society, so that if you were to consume it, or be around someone who has consumed it, you'd known what to expect. So it doesn't take the popularity of a certain drug, if it would tobacco would be the first one, because it causes the most harm overall, due to it's harm, addiction potential and level of usage.
So these charts do show the actual danger of of each one of these drugs using objective evidence rather than just the usage statistics.
It is shocking to most people, but alcohol is a drug and it is incredibly harmful to both the user and people around the user. And the reason why it's so popular, legal and widespread is because it has been a part of the western culture for so long and alcohol industry is more influential than most other drug industries.