I used to be a “frontender” that was HTML, CSS and Jquery when backend was PHP or .NET. The meanings have blurred but I believe the needs stay the same, the split between presentation and logic.
But there’s something about just HTML and CSS that’s frowned on, it’s seen as an entry level skill and I think people devalue it because of that. It’s got a shallow learning curve if you want cobble something together but to master it takes a lot of effort, especially if you want quality and management of the UI. So while the environment is wrong, I would still advise to adding some other highly skilled tools to your toolbox as well. I’ve chosen the design root but it’s been a long time building up to that, again a major skill set that looks easy but mastery is hard.
I totally agree that ‘we’ are fuelling this. Because every job I ever see fuses both HTML and CSS with Angular knowledge or React. React does have JSX though a merge of writing HTML and JS so I can see some thought behind that still we shouldn’t marginalise a perfect good SET of skills.