> It's incredibly far away from doing any significant change in a mature codebase.

I agree with this completely. However the problem that I think the article gets at is still real because junior engineers also can't do significant changes on a mature codebase when they first start out. They used to do the 'easy stuff' which freed the rest of us up to do bigger stuff. But:

1. Companies like mine don't hire juniors anymore

2. With Copilot I can be so much more productive that I don't need juniors to do "the easy stuff" because Copilot can easily do that in 1/1000th the time a junior would.

3. So now who is going to train those juniors to get to the level where we need them to be to make those "significant changes"?