Sloppy technical design ends up manifesting in bugs, experiential jank, and instability.

There are some types of software (e.g. websites especially), where a bit of jank and is generally acceptable. Sessions are relatively short, and your users can reload the webpage if things stop working. The technical rigor of these codebases tends to be poor, but it's generally fine.

Then there's software which is very sensitive to issues (e.g. a multi-player game server, a driver, or anything that's highly concurrent). The technical rigor here needs to be very high, because a single mistake can be devastating. This type of software attracts people who want to take pride in their code, because the quality really does matter.

I think these people are feeling threatened by LLMs. Not so much because an LLM is going to outperform them, but because an LLM will (currently) make poor technical design decisions that will eventually add up to the ruin of high-rigor software.