In the professional projects I have done the majority would have been possible to do with HTML/CSS/JS. The only reason not do that was that customers typically

In the professional projects I have done the majority would have been possible to do with HTML/CSS/JS. The only reason not do that was that customers typically need some sort of backend and that was back then just simpler to do by other means. But there is quite some projects where you don't even need that. Learning HTML/CSS/JS is a good idea as ultimately any framework or serverside code will interact with some combination of the three. Having a strong grasp of how HTML/CSS/JS work is the perfect foundation for learning something that runs serverside. And you get there by building projects that predominantly lean on the three. Whether they are private or professional, who cares as long as they are cool and someone learns something from it?