dynamic content to render in twig using symfony

Question

What I would like to achieve is to output some dynamic text coming from DB filled with unpredictable number of placeholders to be filled with some query parameters.

Basically it is an automation/notification system whereby upon user or admin's interaction with the website, some automation tasks will get triggered and added to DB. My closest shot at almost handling it is by using twig |replace filter in connection with twig extension. The problem is that I get to see the replaced text with the raw data not their parsed value. I guess it's better to look at my code. Your help is greatly appreciated.

DB Schema 'AutomationMsgTemplate, aka: amt'

raw_msg(text type) | format_keys(text type) | format_values(text type)
You are %USERNAME%  |      USERNAME         |         row.user.username
%No% %ORD_STATS% created |    NO, ORD_STATUS |        row.notif.x, row.order.y

My Service 'MsgFormatHelper' (facilitating twig ext)

public function renderMsgUsingSprintFormat(AutomationMsgTemplate $amt, GeneratedAutomationTask $gat): array
{
    $formatter_keys = $amt->getFormatKeys();
    $formatter_values = $amt->getFormatValues();

    $formatter_keys_arr = explode(",", $formatter_keys);
    $formatter_values_arr = explode(",", $formatter_values);

    $formatter_ready = array_combine($formatter_keys_arr, $formatter_values_arr);

    return $formatter_ready;
}

Twig extension

    class AppExtension extends AbstractExtension implements ServiceSubscriberInterface
{

private $container;
public function __construct(ContainerInterface $container)
{
    $this->container = $container;
}

public function getFunctions(): array
{
    return [
        new TwigFunction('msgSprint', [$this, 'renderMsg'])
    ];
}
 
public function renderMsg($amt, $gat): array
{
    return $this->container
        ->get(MsgFormatHelper::class)
        ->renderMsgUsingSprintFormat($amt, $gat);
}

public static function getSubscribedServices(): array
{
    return [
        MsgFormatHelper::class
    ];
}

}

And finally inside the twig

{% for i, row in incompleteTasks %}
    {% for amt in row.aet.automationMsgTemplates %}
        // MOMENT OF TRUTH IS BELOW:
       {% set format_arr = msgSprint(amt, row) %}
       {% set processedMsg = amt.message|replace(format_arr) %}
       {{ processedMsg }}

//nope, output is like: You are row.user.username
//sure enough below, as a debug test, works as intended
  {# {% set processedMsg = temp.message|replace({'%USERNAME%': row.ats.studentCourse.student.username}) %} #}

    {% endfor %}
 {% endfor %}