How to add Enable Disable functionality for a referenceBlock in Magento 2

You can try a different approach to solve your issue.
I assume that you are using <referenceBlock name="product_recommendations_pdp" to add a block or execute an action on the specified block.
You can add the ifconfig attribute on your block or action tags.

<referenceBlock name="product_recommendations_pdp">
    <action method="setTemplate" ifconfig="section_name/group_name/field_name">
        <argument name="setTemplate" xsi:type="string"> your_template_path</argument>
    </action>
    <!-- or -->
    <block class="your_block_class_name" ifconfig="section_name/group_name/field_name">...</block>
</referenceBlock>

Use ifconfig attribute

ifconfig will not work with <referenceBlock> tag. So you need to call the block again in your custom layout file and add ifconfig attribute with your config path. The blocks with same name gets eventually merged as one.

<block class="your_block_class" name="your_block_name" ifconfig="section_name/group_name/field_name" template="your_template_path" />