I think this depends on a developer's background before using AngularJS. I've used Spring (Java DI framework) for a while and AngularJS DI was easy to understa

I think this depends on a developer's background before using AngularJS. I've used Spring (Java DI framework) for a while and AngularJS DI was easy to understand. However, the first time I was introduced to the DI concept, it took a while for me to understand it. Some of the complaints about the difficulty of AngularJS DI could be because for some JS developers it's the first time they've been introduced to the concept.