How to get a query odered by N of matching taxonomies?

There is no native function which to accomplish what you need. The only possible solution that I can think of is to make use of usort to sort the returned array of posts from your custom query

You will need to do the following:

• Set you list with the desired tags

• Get a list of the tags a post belongs to

• Return an array with all the tags that match the two arrays

• Count the tags, and store the tag count in an array

• Sort your array and loop through the posts again and display as normal

The functions used here are as follows

• get_the_tags

• usort

• array_intersect

• wp_list_pluck

Here is an example code. Modify as needed

$args = array(
    'posts_per_page' => '-1',
    'cat' => 'YOUR_CATID',
);
$q = new WP_Query( $args );

if( $q->have_posts() ) {
$count = [];
$count1 = [];

    while( $q->have_posts() ) {
        $q->the_post();

        $posttags = get_the_tags();
        if( $posttags ) {
            $tag_slugs = wp_list_pluck( $posttags, 'slug' );
            $relevant_tags = array('tag1', 'tag2', 'etc which translates to end of thought capacity' );
            $matched_tags = array_intersect( $tag_slugs, $relevant_tags );
            $count[$post->ID] = count( $matched_tags );
        }else{
            $count[$post->ID] = 0;
        }
    }

    usort( $q->posts, function ($a, $b) use($count) {

        return ($count[$a->ID] < $count[$b->ID]) ? 1 : -1;

    });

    rewind_posts();

    while( $q->have_posts() ) {
        $q->the_post();

        //Display your loop elements

    }
}