This is an easy theory to prove; if AI was anywhere close to a senior engineer, we'd see the costs of software development drop by a corresponding amount or quality would be going up. Not to mention delivery would become faster. With LLMs being accessible to the general public I'd also expect to see this in the open-source world.

I see none of that happening - software quality is actually in freefall (but AI is not to blame here, this began even before the LLM era), delivery doesn't seem to be any faster (not a surprise - writing code has basically never been the bottleneck and the push to shove AI everywhere probably slows down delivery across the board) nor cheaper (all the money spent on misguided AI initiatives actually costs more).

It is a super easy bet to take with money - software development is still a big industry and if you legitimately believe AI will do 90% of a senior engineer you can start a consultancy, undercut everyone else and pocket the difference. I haven’t heard of any long-term success stories with this approach so far.

This sounds like a comment from someone who has tested it in a limited capacity such as small blog sites or side projects that did not need to be maintained

Yes, you are right

I'm yet to see that production-grade code written by these production-grade models;