Why is my Layout XML update nor working?

Question

I'm going completely mad here. I have the following in "Layout Update XML" in one of my categories:

<referenceContainer name="content">
    <block class="Us\Tastemakers\Block\Tastemakers" name="category.tastemakers" template="Us_Tastemakers::tastemakers.phtml" before="-"/>
</referenceContainer>

I then have the following files:

app/code/Us/Tastemakers/Block:

<?php
namespace Us\Tastemakers\Block;
class Tastemakers extends \Magento\Framework\View\Element\Template
{    
    protected $_productCollectionFactory;

    public function __construct(
        \Magento\Backend\Block\Template\Context $context,        
        \Magento\Catalog\Model\ResourceModel\Product\CollectionFactory $productCollectionFactory,        
        array $data = []
    )
    {    
        $this->_productCollectionFactory = $productCollectionFactory;    
        parent::__construct($context, $data);
    }

    public function getProductCollection()
    {
        $collection = $this->_productCollectionFactory->create();
        $collection->addAttributeToSelect('*');
        $collection->setPageSize(3); // fetching only 3 products
        return $collection;
    }
}

And app/code/Us/Tastemakers/view/frontend/templates/tastemakers.phtml

<?php

/* *
 * @var \Us\Tastemakers\Block\Tastemakers $block
 */

 echo 'Hi there. I\'m here. I\'m a tastemaker';

// $productCollection = $block->getProductCollection();
// foreach ($productCollection as $product) {
//     echo "Inside view <pre>";
//     print_r($product->getData());
//     echo "</pre><br>";
// }

But none of my text gets displayed anywhere. I have done a complete cache:flush for good measure.

I'm completely going mad here. I must be missing something. Please put me out of my misery!

Update

I have the impression that something is stopping the admin's layout update xml from doing anything at all:

I have now added the same XML block to the catalog_category_view.xml and it works fine.

However, no layout update xml in the admin backend have any effect.

Here are two I have tried:

<referenceContainer name="content">
            <referenceBlock name="category.tastemakers">
                <arguments>
                    <argument name="skus" xsi:type="string">1,2,3</argument>
                </arguments>
            </referenceBlock>
</referenceContainer>

<referenceContainer name="content">
        <referenceBlock name="category.tastemakers"  remove="true"/>
</referenceContainer>

It literally doesn't do anything.

Answer 1

Remove the before="-" and see if it works.

Or check on the web page source in case it's putting the text somewhere on the page.