So yii 3 is basically a clean up of yii 2 from all built-in extra library, and devs are free to include those with composer. No?

Seriously yii.
Go for Laravel

Simplest

Lumen or Silex

Well you can obviously edit your composer file to get only what you want..

@Lyniven i meant that the rewriting of yii2 consist in removing third parties stuff and making a modular core

@zotigapo i tried laravel, hated it since the very first second. So complicated for nothing. Yii is so simple.
But this is highly subjectiv, u find it easy if "you would have done it this way yourself", so everyone has his coding style

@zotigapo it's like i am in love with angular 7 and hate so much react. Lol.