Hard to say, because it depends on what you are looking for. I took a look at the public view of offerings, and they do have a lot of stuff. The card tutorials seem to teach you how to make a specific card, and I assume you can carry over the basic ideas to your own projects.
Maybe 20 dollars a month for months and months is a lot, but from what I saw when I looked, you can cancel at any time. So you could enroll, watch a ton of tutorials for a month, and then cancel. You might get a lot for your 20 dollars if you did that.
Also: Do you like the projects they show? If they are up your alley, it might be useful to do. If not, then it would certainly be a waste.
While I do agree that a person could theoretically learn just about anything for free on the internet through blogs and YouTubes, searching things out takes time, and once you find things you have to take more time reading or watching to see if they really explain things completely, and there are lots of things that you might not even know to search for but would find in a website like the one you posted about.
There's an advantage to having something comprehensive all in one place. If you are curious and can afford the 20 dollars for a month, why not try it?