Even managed solutions are just mitigations, the "problem" is coding. Computer programs can do anything. This was gated before by knowledge, only coders could effectively write software, including malware and poor-security software. Now anybody can write software.

The corporate computer is a locked-down environment, the set of actions you can perform are limited. They ideally should be the actions you need to do your job, and nothing more. Any method of writing and executing code breaks that wide open - you can now do anything, given enough time and effort. Now the time and effort floors have fallen, too.

Claude Managed Agents might prevent the agents themselves from doing something nefarious, sure. But that was never the draw of AI. The ideal use of AI is doing the least amount of stuff with AI, and the most amount of stuff with code. Asking AI to sort my email? That's good, but writing a program to do that is better. Asking AI to do statistical analysis of my trades? Again, sure, but it's even better to write a program to do that.