But if the time it takes an engineer to build any one thing goes down, now there are a lot more things that are cost effective.
Consider niche use cases. Every company tends to have custom processes and workflows. Think about being an accountant at one company vs. another -- while a lot of the job is the same, there will always be parts that are significantly different. Those bespoke processes often involve manual labor because off-the-shelf accounting software cannot add custom features for every company.
But what if it could? What if an engineer working with AI could knock out customer-specific features 10x as fast as they could in the past. Now it actually makes sense to build those features, to improve the productivity of each company's accounting department.
It's hard to say if demand for engineers will go down or up. I'm not pretending to know for sure. But I can see a possibility that we actually have way more developers in coming years!