I don't see why the developer that builds the interaction with the backend can't be given directly the design and turn it into HTML and CSS himself.

I wouldn't expect the developer to be able to come up with a good web design with the right choice of colors, spacing, etc. but I would expect that given a design he can both turn into HTML and CSS and split it into components.

That is how we organized in several teams I've worked, and there was never any issue.

I have seen however developers who do frontend work who know hardly any CSS and are even proud of it, and that is just not productive.

I used to work in an architecture team and sometimes I would get support requests from development teams because someone couldn't move a button 30px to the right, literally.

I think if someone is a frontend developer, they should be able to write their own HTML and CSS, besides knowing Javascript and a framework like React, Angular or Vue.