What you lose is control. Even in the case of an actually-intelligent agent, if you task a subordinate with producing a document for you, they are going to come up with something that is different from exactly what you had in mind. If they are really good, they might even surprise you and do a better job than than you'd have done yourself, but it still will be their vision, not yours.

Your notion of a "mortal wound" to the software industry seems to assume that today's SaaS portals are the only form that industry can take. Great software is "tool calls for agents". Those human agents who care about getting exactly the result they want will not be keen on giving up Photoshop for Photoshop-but-with-an-AI-in-front-of-it.