Agree. It should fall on to developers to decide what to do = whether tackling tech debt is viable solution (whether making decision on their own or talking to people that can make such decision) or not. If, however, you're told "here is a codebase that you're seeing for first time, fix this error" and you simply cannot make the decision, even prior to LLMs you'd put a bandaid on it. Or at least - that's the standard approach = fix now, refactor later, where later in my experience never happens (sorry for this train of thought).
I don't think this is anything new, nor LLMs are to blame here. Although - LLMs want to make you happy, or maybe they don't think about what user actually needs, just how to accomplish the goal that was stated; they do stuff without asking questions (unless you constrain them or plan first). I've actively put in a hook for my agent to not make decisions on their own and ask me when it detects it's about to make a decision.
Agreed, it is not at all a new problem. The enterprisey codebases I’ve encountered are ones that have chronically had no clear owner, or constant ownership churn. I have been in that position before, and I also decided to make the code even more bloated for the same reason: I did not and was not going to have the time to learn the system well enough to safely do a better job.
I think where a lot of people run into problems with the KISS principle is they conflate simple and easy. More often than not, simple is hard. Which is maybe a soft reason why agentic coding, which is all about trying to make every task easy, leads so consistently to complexity and bloat.