get_users()
is a convenience wrapper around WP_User_Query. Maybe you can use that directly, e.g.
$user_search = new WP_User_Query(
array(
'meta_query' => array(
'relation' => 'AND',
array(
'meta_key' => 'last_login',
//'meta_value' => 'DATE_SUB(NOW(),INTERVAL 7 DAY)',
'meta_value' => date('Y-m-d H:i', strtotime('-7 days')),
'meta_compare' => '<=',
'type' => 'DATE',
),
array(
'meta_key' => 'email_not_logged',
'meta_compare' => 'NOT EXISTS',
)
)
)
);
And then look at the SQL it generates by printing $user_search->request
?