I started learning Japanese around 8 years ago, and I've never been a fan of saying it's "the most difficult language to learn." It's like learning anything else, if you enjoy learning it and are motivated enough, you'll get better. Also I'm surprised when people assume the grammar is difficult - to me, the "flexible grammatical structures" as mentioned in the article are a good thing because it gives you more leeway…
The one downside is that they are still meant to be used in a classroom, so there are a lot of exercises that expect you to work in groups or pairs. Of course there are plenty of ways to find a study group online these days.