I think a lot of things agents do is wrong, but No response means no doesn't bother me from anyone, and some magazines have had this policy for twenty years or more. So have some book publishers.
Auto-responders are a pain in the ass, an invitation to spam, and not always reliable, at that. Using auto-respond is fine, if you have a sophisticated system set up, but few agents or editor have such a system, and don't need one.
If you pay attention to submission guidelines, the agent's spam folder is not going to snatch your e-mail, and if it doesn't arrive at all, and good e-mail system will tell you it wasn't delivered.
It's just never bothered me. Wait your two months, or whatever the guidelines say, and move on. Agents and editors are often overworked, often have no one else who can handle rejections, and deal may have to deal with thousands of writers.
I understand wanting closure, but the time factor often is more important than any individual closure. If an agent or editor had to deal with ten writers per week, I could understand the frustration. But when an agent or editor has to deal with hundreds per week? Nope.