I feel like I'm not using to max the language and its features. Most of the tutorials on the web are for beginners even the advanced classes are not enough advanced for me. I feel like I plateau'ed.
I would highly recommend NOT studying advanced syntax features, but rather what architecture ideas can be used and what are Android best practices:
Hands on learning is also great. If you build an app with a networking library connected to a public API that uses Room for a local database you will learn a lot about coroutines. If you use layered architecture like the docs describe you will learn even more and it will not be too easy. There are great Google tutorials that are hands on and walk through the libraries:
Another idea is instead of researching “Advanced Tutorial for xyz” try searching “Best practices for xyz” and see what resources you find. I did that with coroutines and got some pretty detailed docs:
Lots of people publish on Medium their latest experimentations and findings, and if you make sure it’s a reputable author like a Google Developer Expert you can learn a lot there too.
Your goal with any tech stack isn't to use its most complicated syntax or exhaust its feature pool: It's to build quality software for users at as large a scale as possible.
You can't really do this with tutorials and courses: Those are just meant to teach you how to get stuff working. Getting stuff working is just the first step - Once you get to mid-level, these resources aren't very useful anymore. Once you get to senior, your returns with these will drop to pretty much 0.
I'm an Android engineer, and I've been an Android lead for almost 10 years. In 2021, I was making $750k per year doing Android development. I also don't really know what a coroutine is.
Coroutines, like everything else in Kotlin and Android, is just one way of many to build features and get stuff working. This doesn't make it inherently it a "high-level" Android technique or a requirement to be a stellar Android engineer.
If you really want to get better at Android, you should care about these metrics instead:
I go extremely in-depth about what it takes to write high-quality code and how to get better at it here: "How to Learn/Practice Clean Code, particularly by oneself?"
I also highly recommend these if you haven't watch them already:
Just like any topic: use them. Then realize all these are just ways of writing things.
The way to improve isn't by writing code but realizing how they work, why they work, and why they're used, and how things can be done better.
You should not be focusing on language and features. You should be focusing on understanding what you're writing, why, and most importantly, how to be as efficient as possible at figuring out what you need to write.
That's the difference between coding and engineering.