Really? Most of the time?
I find I spend an enormous amount of time on boring stuff like connecting VCC and ground with appropriate decoupling caps, tying output pins from one IC to the input pins on the other, creating library parts from data sheets, etc.
There's a handful of interesting problems in any good project where the abstraction breaks down and you have to prove your worth. But a ton of time gets spent on the equivalent of boilerplate code.
If I could tell an AI to generate a 100x100 prototype with such-and-such a microcontroller, this sensor and that sensor with those off-board connectors, with USB power, a regulator, a tag-connect header, a couple debug LEDs, and break out unused IO to a header...that would have huge value to my workflow, even if it gave up on anything analog or high-speed. Presumably you'd just take the first pass schematic/board file from the AI and begin work on anything with nuance.
If generative AI can do equivalent work for PCBs as it can do for text programming languages, people wouldn't use it for transmission line design. They'd use it for the equivalent of parsing some JSON or making a new class with some imports, fields, and method templates.