Never Underestimate HTML
Writing HTML in itself isn’t that hard, no.
But: building user interfaces by elegantly composing this language’s features with CSS, creating pleasant designs and user experiences worth remembering requires experience and skills that should not be underestimated. Neither should HTML; it’s one of the languages—if not the most important one of them all—that shape the web.
Web browsers can be incredibly forgiving in terms of displaying content to the user, so mistakes can go unnoticed. But those mistakes can cause problems with accessibility and many other things. Writing good, accessible HTML takes skill and should never be discounted.