Justin Smestad's piece on evalcode.com makes a blunt economic case against the "AI replaces juniors" talking point. Forget mentorship. Forget moral obligation. This comes down to leverage. When a senior engineer asks for a 40% raise, your negotiating position depends entirely on whether you have mid-level people ready to step up. No pipeline means no options. You pay or you scramble. He draws a parallel to small businesses closing not from failure but from owners retiring with nobody to hand the keys to. The apprenticeship model existed for centuries because without it the trade died with the master. This 'learn by doing' pipeline is threatened by autonomous agents handling workflows that were previously manual training grounds.
Where it gets uncomfortable: Smestad points out that senior software engineers are uniquely positioned for financial independence. After a decade of public-company equity and reasonable spending, plenty don't need the job. When someone who can afford to retire asks for a raise, you have zero leverage. They'll actually walk. Your senior team becomes a group of volunteers who know exactly what you'd pay to replace them. That dynamic only works in management's favor if there's a bench of motivated people coming up behind them.
The junior role will shift. Less boilerplate, more reviewing AI output, learning when the agent is making a plausible mess. But the pipeline need doesn't disappear because first-year tasks change. Shopify, a company betting hard on AI, keeps hiring early-career engineers. Not charity. Self-preservation. Instead of relying solely on AI, these new hires must exercise human judgment and taste to ensure quality.