It only takes two or three unreviewed prompts like "the page loads slow, plz fix" for you to end up with a tangled mess that even the agents can't productively work with.

Take a look at the Reddit forums for vibe-coders - now that a bunch of them have been hacking on things for 3+ months there's a growing awareness there that you hit a wall. Here's the first post I found from just searching "reddit vibe coding wall", it's a great illustration of the genre: https://www.reddit.com/r/vibecoding/comments/1sabdw3/anyone_...

Software development is really, really hard. Coding agents can get you a surprisingly long way, but if you want to build real software for real people you quickly find that you DO need that domain expertise.

The agents may type all of the code for you now, but you need a huge amount of skill to clearly tell them what to do, confidently decide what to do next and credibly present software that works for other people to use.