The instructor is correct that you would need to build a custom theme if you want to integrate it better with the WordPress backend. There are two types of themes, which are:
Classic Themes: Despite the name they are still modern themes, but they use code more similar to the tutorial you were following and are written mainly in PHP, thus allowing you call specific data from various parts of WordPress to be displayed wherever you want it. They are much more flexible and allow for more fine-grained design than Block themes.
Block Themes: Let you create templates that integrate with the Full Site Editor (FSE) that has recently landed in the WordPress core. They mainly use HTML with a few other techniques, but they require you to use the Gutenberg builder to manage all of the content. Essentially the final site is built entirely out of blocks.
There are pros and cons to each but if you want to learn how to create a custom WordPress theme, you would first need to decide which type of theme you want to create and search for tutorials that teach you, or review the official Theme Handbook. You can definitely find good free tutorials all over the internet for either type of theme, but purchasing someone’s course would probably teach you quicker, as well as offer updates for future best practices and access to the instructor for questions.
Block themes are probably easier to learn how to create, particularly in a visual way, but Classic themes will let you do anything you want to the design.
If you want to avoid coding altogether, you can look into any of the various page builders that work with WordPress with a Google search. I personally like Oxygen but other popular ones include Divi, Elementor, BeaverBuilder, Bricks, Breakdance, and many others with various features and price points. Most of them have a demo or a freemium version you can try, and they all have strong communities – largely in Facebook groups – where you can ask questions.
None of them are as flexible as learning to build a Classic theme, but many of them come close enough that you can definitely build creative sites, and all of these options, including a custom Block theme, would let you create the screenshot you shared.