[pacohope]

In addition to what the others have written, let's not forget the abstraction of storage and networking. Docker let's you present virtual network interfaces to the software, so the config can be the same everywhere. Every container thinks it's listening on port 3000 on its local host. Without Docker, if you want to run 2 or 3 different bits of software on the same host but listening on different ports, that's has to be part of the software config, not external to the software config. With Docker, every instance of the software inside a container can have the same network config, but external to the container you can do whatever network jiggery-pokery you want to line it up.

Likewise Docker volumes and mount points. The software gets an abstracted filesystem that's actually a "volume". Could be a chunk of local filesystem, an NFS mount, whatever. The software doesn't need to know. It just acts like it's the only software on the "system" and writes to any path that it can find. It can't corrupt any other containers also running on the same host by writing global configuration files or making "system-wide" changes because those system wide changes are contained to the container.

Docker also abstracts a ton of sysadmin/deployment type tasks. I have 1 container of app X running on host A. There's a load spike. I want a second instance of app X running on host B. Ok. Load spike is over, I want to get rid of the instance of app X on host B. Docker makes this kind of dynamic deployment/destruction automatable via APIs and there's huge libraries of software out there to do it. I don't know about the .NET packaging/deployment (NuGet, etc.) and whether that's as easily done.

It sounds like you know a lot about .NET, and I know very little. So it's entirely possible that Microsoft has solved the network and storage abstraction in ways I don't know about. In that case, if you don't NEED Docker, because you have this homogenous environment and effective isolation controls built into it, be comfortable in your lack of need.