The only things that have ever worked for me to learn new technologies and techniques are

1) Taking on a major project in the language/technology

2) Classes

and I've learned a lot more from projects than classes. I've never found textbooks, slides, web pages, and the like, to be useful absent a concrete project to anchor my learning to. That said, if I do have a concrete project, then written materials such as books are hugely useful in accomplishing that project.

In brief, I advocate a sink or swim approach. For instance, if you want to learn Android programming start building a real Android app. Read the first couple chapters of a good Android book at the get go, and some of the official tutorial on the web, and then start coding. Refer back to the book, the tutorial, and the API documentation as needed during development.

After you've completed 2-3 projects in the new technology you'll have the basics down and start to see mistakes and flaws in your early understanding. At this point it's good to attend talks and read books and articles about best practices in the technology. E.g. if you're building PHP web apps, this is when you'll start learning about REST instead of just hacking together whatever seems to work. If you're programming in Java, this is when you read Effective Java. But first you need to have a basic familiarity with your tools and know how to use them, before you can start learning how to use them as a master craftsman.

Of course I have a sample size of one here. Different people learn in different ways, and you may learn differently than I do. But this is what has consistently worked to keep me at the forefront of every technological wave I've chosen to surf for about 20 years now.

I am not sure how much the "learning in depth" can be avoided. This may be a prejudice, but it seems to me that software development typically really has a lot of inferential depth compared with... I don't know... plumbing.

In addition to this, software development is in motion. You can use the same screwdriver for decades, but software frameworks are developed so quickly that even remembering their names becomes a difficult task. (I can't even remember all frameworks in Java.) So it's not like they can't be taught effectively... it's more like there is so much of them that the few people able to teach them effectively didn't have time to learn the topic and write a book on the topic yet. (Maybe they will do 5 years later, but then you will want to learn something different, or a new version different from the old one will appear.)

If -- somehow -- we could choose the best programming language, or just say best 10 programming languages, two or three frameworks for each of them, remove everything else, and freeze the progress... then within 20 years we would discover efficient ways of teaching them, so that how we learn them today would probably seem completely ineffective in comparison.

But that is not going to happen, for many reasons, at least during the following decades. (Some of those reasons are good, such as progress, some of them are bad, such as reinventing the wheel either because of ignorance or for profit.)

Anki decks are great when you don't go into depth. Or when you go into depth using some other source (such as a book), and then use Anki decks to memorize what you learned there.

In my opinion, a good way to learn is to get a lesson from someone who really understands the topic, knows how to explain it, and especially is later available to answer your questions. A week of education this way easily beats months spent reading online tutorials written by people who overestimate their own understanding of the topic, or just don't care and do it for adsense (w3schools, roseindia...). But in my experience people are usually averse to pay for this. (It's like in their cost-benefit calculations they assign almost zero costs to their time and they horribly understimate how much time would they need.) The second best option is to read a book on the topic, or perhaps a few of them.

My current stack is linux, apache, python, django, dynamo, js, backbone

This does not provide as much information as it seems to do. I can install Linux (using the installation wizard) and run a few programs from the command line. Linus Torvalds invented Linux and probably knows everything. Where are you on this scale? Where are you on the Python scale: are you able to write "Hello World" or what exactly? How about the many things you did not mention here, such as: do you understand algorithms, computational complexity, formal languages, automata, functional programming, etc.? That could make a huge difference in choosing the right way to learn a new language.

Also... what exactly are you trying to achieve? Add a few keywords to your CV, or some other specific goal?

The #1 skill I've needed to foster since I began to program professionally is the skill of -not having to know exactly what is going on-. It's a very difficult skill to foster.

I work with, no joke, around 250 different technology frameworks/stacks. I don't get the luxury of only having to work with one operating system. If a client uses it, I have to know how to work with it.

The trick isn't expertise. It's a generalized knowledge of how people tend to construct frameworks, combined with -really good- debugging tools and skills, and high levels of Google-Fu.

The first part - understanding how people tend to create these frameworks - is the most important. If you can get a strong grasp of this, you're 95% of the way towards understanding any given framework.

Another important skill is knowing when to give up on a framework as being incomplete/unworkable/unmanageable. Those 250 are just the frameworks that have made the grade.