A few things: The memory and SSD can't be replaced by the user, meaning pro users are looking at potentially significant downtime if these items fail. The machine isn't serviceable at all without removing a screen attached by adhesive, a process that can cause breakage. The screen is also small by the standards of many pro users (I've not personally used a screen below 30" in years), and the design of the VESA mount is reportedly problematic. There are no Nvidia BTO options, and therefore no CUDA support. There are numerous reports of the T2 chip causing USB audio issues. The AIO design also limits the thermal headroom of an ostensibly "professional" workstation.

It is great product. But there are few compromises:

1. Thermals. Apple prioritized silence over performance. So they like to run cpus at high temperatures and start fans only than it is absolute necessary. It limits cpu clocks and performance. And although it has great cooling solution it worse than it could be that if it was just standard desktop. And it uses intel cpus that are pretty hot because they use older technology node.

2. CUDA. There are no nvidia support for Mojave if i am not mistaken. So there isn't support for CUDA. It should make some stuff very hard or impossible. For example ML training.

3. Price. It is very expensive. Hackintosh build including great monitor with intel + amd gpus will be twice as cheap.

Not the parent poster, but I already have a desktop machine with no compromises. It's a custom-built arch linux machine with the best screen, keyboard, and mouse I could buy.

Desktops are solved, we don't need a savior for desktops because the modularity allows us to combine the best parts from various manufacturers.

We need a savior for laptops where the keyboard, mouse, screen, and components are all embedded, and there's no way to separate them.

I consider the iMac a convenient machine but it's a bit like buying a tv with a vcr built in and a keurig machine built-in too.