Artisan::queue('email:send', [
'user' => 1, '--queue' => 'default'
]);
The '--queue' => 'default'-part in your example doesn't automatically queue the artisan command. This is just an option which is passed to the email:send command. The command would then have to read the option and implement the queue itself (https://laravel.com/docs/master/artisan#defining-input-expectations)
May I ask, what exactly you want to accomplish and why? Why do you want to schedule an artisan command?
Why don't you use Jobs? (It seems you already have experience with jobs)