I don't think it replaces a junior, but it raises the bar for the potential that a a junior would need to show early, for exactly the reason you mention. A junior will now need to be a potential senior.

The juniors that are in trouble are the low-potential workhorse folks who really aren't motivated but happened to get skilled up in a workshop or technical school. They hopped on the coding wagon as a lucrative career change, not because they loved it.

Those folks are in trouble and should move on to the next trend... which ironically is probably saying you can wrangle AI.