Excluding products in shop by meta data

Hello.

We have some discontinued products which have a meta tag of “_discontinued-product”. When these values are set (to anything), we want to exclude it from the shop loop.

We have tried this by modifying our functions.php file with variations of this entry:

function remove_discontinued_4(){
    
    if( ! is_shop() ) return $meta_query;

    $meta_query[] = array(
         'key' => '_discontinue_product',
         'compare' => 'NOT EXISTS' 
        );

    return $meta_query;
}

add_filter( 'woocommerce_product_query_meta_query', 'remove_discontinued_4', 10, 2 );

This WORKS, but we have alot of products (around 2000) plus variations – so this becomes VERY VERY slow, adding about 30 full seconds to the page load time, which is unacceptable for the user experience.

Is there a way to do this through woodmart that I’ve missed? Or perhaps you have a suggestion on how to achieve this without such a huge lag?

Thanks in advance!
~S