I don't think frontend development is any less complex than systems engineering.

> What will stay, is human level systems engineering, Running things, designing etc

In fact I think it might be the other way around.

I'd expect systems to be slower to change and subject to their own hard dependencies on consistency. That makes them easier for a language model to imitate.

I'd expect frontend dev to move faster and subject to a never ending churn of non-technical wants from sales and marketing. The huge amount of boilerplate is an attempt to handle the few patterns that exist in an otherwise very sparse space where one design is miles away from another and much glue is required to accomplish the task. Messiness here is not due to inherent complexity, but apparent complexity since things are never allowed to converge onto something more coherent.