Like many crafts (painting, music, etc) the true test of great software is time. Not because of taste, but because software is a living artefact that must evolve.
Only over time does a human developer realise they have "painted themselves into a corner" and chosen the wrong abstractions. And it will be the same with vibe coding (i.e. where code is not architected and reviewed exhaustively by a human).
Because companies won't surface their internal codebases, the most likely signs of such problems with be the reliability of applications and services. I don't know if recent outages are indicative of changes in code practice, or just coincidence, but we'll find out over time.
Agents aren't yet strong general reasoners - they are good at reasoning in the shape of their training corpus - so it's essential that important code is reviewed by human experts.