Zend certified PHP/Magento developer

layout/default.xml doesn’t seem to work in a child theme from Luma

I have created a new child theme from Luma. The admin panel recognizes that it’s registered and I have set it up to be used for my store.

One of the things I tried to achieve was changing the logo for a store, tried to define it in default.xml, and flushed the cache, but nothing changed on the frontend.

Afterward, I tried to insert a container with a block on top of the header, but also no sign of any changes.

What exactly I am doing wrong? Can’t seem to figure it out with just the help of Google.

Files structure

📦frontend
 ┣ 📂MyVendor
 ┃ ┗ 📂MyTheme
 ┃ ┃ ┣ 📂etc
 ┃ ┃ ┃ ┗ 📜view.xml
 ┃ ┃ ┣ 📂layout
 ┃ ┃ ┃ ┗ 📜default.xml
 ┃ ┃ ┣ 📂templates
 ┃ ┃ ┃ ┗ 📜top_message.phtml
 ┃ ┃ ┣ 📂web
 ┃ ┃ ┃ ┣ 📂css
 ┃ ┃ ┃ ┃ ┗ 📂source
 ┃ ┃ ┃ ┣ 📂fonts
 ┃ ┃ ┃ ┣ 📂images
 ┃ ┃ ┃ ┃ ┗ 📜my_logo.png
 ┃ ┃ ┃ ┗ 📂js
 ┃ ┃ ┣ 📜registration.php
 ┃ ┃ ┗ 📜theme.xml
 ┗ 📜.DS_Store

default.xml

<page xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:View/Layout/etc/page_configuration.xsd">
    <body>
    
        <referenceContainer name="header.container">
            <container name="header.message.wrapper" htmlTag="div" htmlClass="header-message-wrapper">
                <block name="header.message" template="MyTheme::top_message.phtml" class="MagentoFrameworkViewElementTemplate" />
            </container>
        </referenceContainer>

        <referenceBlock name="logo">
            <arguments>
                <argument name="logo_file" xsi:type="string">
                    images/my_logo.png
                </argument>
                <argument name="logo_alt" xsi:type="string">
                    Awesome logo
                </argument>
            </arguments>
        </referenceBlock>

    </body>
</page>

top_message.phtml

<p>Free shipping for all orders.</p>