I think one thing that this chart sort of causes you to forget is how much of an impact motivation can have. For example, someone going to school to learn a language because it's part of government curriculum, or even after school because your parents want you to will probably have a much harder time learning than someone who is learning on their own will.
As an English speaker, I had a VERY hard time with French, mostly because we were forced to learn it in school and I never really cared. I spent my whole life thinking that learning a language would be boring and near impossible without immersion. But now I am learning Russian simply out of my own interest, and am having a completely different experience with it. I'm using free resources I've found off the internet and making a point to try and speak it with friends and watch tv shows from Russia, and I'm finding it infinitely easier and more fun than French ever felt! I see a lot of comments by people saying "oh I've always wanted to learn that, but this chart says it's hard" - my point is, don't put too much weight in to this chart. If you want to learn it, you should try, you might do better than you'd expect!