Resources on 3D animation is limited because it's a very high level art to get into. That is to animate well you will need good rigs and content available just to get started.
Not many people are even proficient enough to say much substantial on this topic since the bulk of animation work in the industry is team colaborations revolving heavy around motioncapture systems.
For handmade animation the subject is hard to cover in written tutorials and too lengthy a process to demonstrate very well even on video.
Making proper animation tutorials is a lot more labor intensive and edit-heavy, and requires a much more thought out approach than say showing someone how to model stuff.
Because it's hard to package in a digestive form it's more the kind of thing you'd mentor someone to do. Not something you'd whip up in your spare time and post for free on the internet.
On the art side, animation in general, is one of those things where the basics of the subject is really all there is to it.
It's very simple to pick up to get started out, yet these core basics need to be implemented so subtly that you will need to just grind your craft endlessly untill you've really mastered them.