My thought on why people especially juniors are just delivering slop: Why bother with quality? Why bother with the craft? When it will be disrupted by the next tool/AI model/etc in the next few years anyway? Just think short term - will this slop get you through the PR and tick a short term box? If so success - might not have a job long term anyway due to all the AI stuff. In fact if I keep ticking boxes I'm more likely to last than the other person given more job incentives. Just get paid today.
In your example a QA that is skilled at testing websites should pick up CORS issues for example. And the models will keep getting better and eventually give them harnesses too - and we SWE will slowly automate everything around this because the only lifeboat left for your career is to cash out hopefully by disrupting yourself (no unions, professional bodies, etc).