On D11 (PHP8.3), the module's settings form throws this error:
ArgumentCountError: Too few arguments to function Drupal\Core\Form\ConfigFormBase::__construct(), 1 passed in /var/www/html/web/modules/contrib/critical_css/src/Form/SettingsForm.php on line 36 and exactly 2 expected in Drupal\Core\Form\ConfigFormBase->__construct() (line 43 of core/lib/Drupal/Core/Form/ConfigFormBase.php).
Install this module on D11 and go to /admin/config/development/performance/critical-css.
Update SettingsForm::__construct() and SettingsForm::create() as required.
I already have a fix, so will create a fork & MR.
Active
2.0
Code
Issue #3484467: Settings form error on D11
Thanks for the report, already fixed and published