I would say - Password only ssh logins; Old / Vuln libs; non tests covered code; XSS and SQL Injection from all the code. - But this is really boring.
AI witch threatens to take over developers occupation - this is more interesting idea for future consideration.
But really I just want to see one thing to be destroyed - idea that creating new tools will solve all the issues (looking at you JS world) instead of improving existing ones or even real deep thinking about the problem beforehand. And then dropping it (new tool) after something new more shiner comes up.