Generally speaking - your technical qualifications value over a replacement hit their peak sometime between 3 and 10 years into your career for most folks. Meaning while you may be particularly skilled, learning one more discipline, stack, technique, or language probably won't let you get a particular job done any better or faster than the next engineer.

Many engineers move to management at this point, which requires that you can mentor and grow a team of engineers, set goals, drive projects to completion, and manage your team through performance reviews.

Folks who stick to the technical path need to become an indispensable piece of technical glue across N teams, keeping them all building in the right direction and not crushing each other. This job requires deep technical knowledge but often doesn't involve a ton of coding e.g. Linus Torvalds.

If a junior engineer showed up with the behavioral qualifications of Torvalds and the technical skill of a junior engineer - they would still be a junior engineer and unable to build trust, guide a team effort, or other activities.