Learning HTML is not the same as learning to write software

At least IMHO they are not equivalent. Why not ?
Html is a design markup language. One focused on layout and presentation. A web designer might use Adobe DreamWeaver to create the specific layout and look of a web site. And never touch a line of PHP, C, Javascript, or whatever language is used to implement the functionality of the web site. Wikipedia points this out on the first line of its entry about HTML where it says

Hypertext Markup Language (HTML) is the standard markup language for documents designed to be displayed in a web browser.


Conversely the developer writing the functionality might never touch a single line of HTML or CSS code to make the layout look any particular way. Layout and design are not necessarily their role.

There are however people who are conversant with both the design language (HTML) and add ons to it (CSS) as well as with certain programming languages that can be used on the Web (Javascript). Usually these are in the “front end” or the Web browser. And it’s not unusual to find someone who understand all of these.

Now there are even people who understand all these technologies that are used in the browser and all the back end technologies used to implement the additional functionality of a web site. Usually they’re known as “full stack developers“.

A person like this has learned the language of web designers, generally html and css, some programming languages, php and javscript are common, more than likely some web based framework for various controls and layout like jQuery or Angular, and usually has some knowledge about databases like mySQL or postgresql for the back end.

EDIT : 12:47 I’ve received a comment offline where a confused reader seems to think I implied that one is more important than the other. I make no claim one way or the other and, in software, they both play an important but different role. An ugly app is an ugly app. And one that doesn’t do what it says just doesn’t and so both are required whether its a successful app, web app, or web site.