The problem with these automated "agents", just call them scanners, is that they only test for known threats. Just as your vulnerability scanner du jour.
Sometimes an attacker does not need more than a flaw discovered and patched 2 years ago. Regularly I still see important systems in my customers' networks vulnerable to MS17-10. But that is covered completely by vulnerability scanning.
What does this supposedly bring to the table? Blue team training? Network detection validation and tests?
If you are a financial institution the groups that want to target you include sophisticated and determined attackers. They will have techniques not adequately covered by these systems. Or they will just invent a new technique. You don't hamstring these operators by endlessly re-sending their C2's traffic through your network sensors! (Or so I keep telling people rabidly interested in "actor emulation"). They are not stupid, they'll just invent a new technique...
Secondly, holes in your monitoring correlate with holes in your preventive security. You can hardly monitor for an exploit you don't know exists. You can't 'simulate' an attacker living of the land.