Comment by bitwize

It's more complex because the tooling optimizes for teams of developers rather than single developers. For example, back in the day it was expected that programmers knew enough of how UI works for their given platform to where they could either drag widgets onto a form (e.g., VB, Delphi) or just code up where they're supposed to go (e.g., Tcl/Tk) and they'd have a UI for their application. These days there's a huge division of labor between how widgets are supposed to look and feel, and where they're supposed to go (designers), what their actions are supposed to be (front end developers), and what state changes those actions represent (back end developers). These are assumed to be done by different people, so the tooling supports each person's workflow, e.g. L^HFigma for the designer, React for the front end, etc.