Ask HN: Given reference design, can any SaaS add styles to raw HTML?

I hate messing around with css and design is a real skill I haven't taken the time to develop yet. I'm wondering if a tool exists that takes inputs: 1) raw HTML, 2) some webpage whose style I like (but don't want to copy precisely). And outputs: HTML with styles applied.

Generally speaking: design resources/tools/courses for busy devs?