How does this compare to say... a $10/mo DigitalOcean Linux VPS that you deploy stuff to with like... Ansible?
So that's one difference. AWS is expensive, and its performance tiers for stuff like networking can be frustratingly opaque, but when you pay enough, you do get more-or-less what you paid for. And fighting DO's networking can get expensive in a hurry, in lost business or technician hours.
As for Amplify vs. Ansible, yeah, dunno.
[EDIT] Incidentally, this isn't the first time I've seen hosting of this general sort fall apart at the networking level—I ran into very similar problems with RackSpace over a decade ago, there was simply no way to come anywhere near taxing the hardware we were paying for before the pipe got saturated, like, there was an order-of-magnitude mismatch between the two, requests timing out en masse while the hardware ("what a good bargain this price is!") was practically idle.
[EDIT EDIT] It's probably no coincidence that it's easy to list and understand hardware specs, but difficult to communicate or evaluate real-world Internet-connected network performance without trying it—so it's probably tempting as hell to scrimp on networking while selling based on bang-for-the-buck in hardware allocation.
With DO we'll have some clients seeing great performance, and others who may as well be on a spotty dial-up connection at the exact same time. Frustrating, and there's not really anything you can do about it except switch to another host. I'd love to know what the story is with 'em.