In my ideal world, theres a UX designer to take in (and mentor in) that work. Perhaps design is baked into frontend work in smaller companies, but every place I’ve worked has had a specialist devoted to that work.
Even I, an infrastructure monkey, can follow a design doc with explicit values for widths, lengths, and font colors, faces, and sizes.
I think that in practice a frontend engineer is still going to be making a bunch of ux and design-oriented decisions during implementation, since no design ever translates perfectly. Botching these over and over really slows things down (or hurts overall quality if they never get cleaned up) compared to someone with enough design sense to improvise and fill in the gaps.
Even I, an infrastructure monkey, can follow a design doc with explicit values for widths, lengths, and font colors, faces, and sizes.