That might be true for agentic coding (caveat below), but AI in the hands of expert users can be very useful - "great" - in building large and complex apps. It's just that it has to be guided and reviewed by the human expert.
As for agentic coding, it may depend on the app. For example, Steve Yegge's "beads" system is over a quarter million lines of allegedly vibe-coded Go code. But developing a CLI like that may be a sweet spot for LLMs, it doesn't have all the messiness of typical business system requirements.