How appropriate is the widespread use of Yii::$app-> in a project?

Question

Yii

Hello
I'm working on a large project on Yii2, I'm still not well versed in this framework. I read somewhere that using Yii::$app is a bad practice in work (they say it is possible, but rarely).
In the current project, I see that Yii::$app is used everywhere.
I want to clarify - is this really a bad practice, or is it normal?

Answer 1

It's bad practice to use Yii for a big project.
If you pick up the project - choose between compatibility (use the coding style that is accepted) and creeping refactoring (gradually change the style to a new one).
In the case when "I don't understand this framework well" - choose compatibility.

Answer 2

it's bad practice to keep the codebase tightly coupled