Ask HN: Docker vs simple DLLs?

I'm already feeling bad for creating yet another docker-related post but I figured f** it, I just don't get the hang of it so somebody pls conclusively, once-and-for all, explain the need for and blessing of docker in a simple, fool-proof fashion:

What I did understand so far is "Docker is useful if you have multiple applications with different versions of the same dependencies running on the same machine, as well as for deploying onto any machine".

MY QUESTION: (Why) don't dynamically linked libraries (.dll) already solve this problem?

I come from the .NET world and there I can run any number of applications all with their respective dependencies, e.g. NuGet packages, as .dll files in their own isolated directories - doesn't this already solve the problem of isolation and avoid dependency-conflicts? This is also easy to ship to any machine as I just compile the whole thing for the respective architecture and then copy and paste it over, set it up as a service/daemon, whatever.

To me a standalone application is simply a directory with an executable and all dependency-dlls in the same directory / some subdirectory. This is already a software-wise isolated application (obv not on the hardware side but lets leave that out for a second), of which I can run multiple on the same system. Why do I need docker on top of that?

I am probably misunderstanding something fundamental here so for the 21375th time, what is an idiot-proof explanation for the need of docker in light of dlls?

Docker helps with two problems DLLs dont:

1) what if I want to run your app on my Linux server and I dont have dotnet set up. I dont want to deal with installing and maintaining dontnet. And I dont trust your setup script

2) You want run a database and message as part of your application, and they aren't dotnet.

How to you deal with resource allocation (memory limits, cpu limits, etc.) ? How to give a different IP address to each application ? What if an application fails and starts filling your disk space and thus impacts others ?

Docker, and the tools on top of that, can make these problems easier

Becuase your solution is specific to your specific software.

Then you have lads who use python who can use virtualenv, and then the ruby ones who use rbenv and then you have the CPP developers which are usually fine but on Tuesday Joe messed up the linker settings and all of a sudden we're not statically linked, thanks Joe.

And then our Java team forgot to tell the sysadmins that they upgraded the JVM version.

The thing with docker is that you just get a complete package with everything delivered directly by the developer and it's very hard to mess up.

Also docker can run applications that aren't shipped by people in your company and also does more stuff (like more sandoboxing and it also helps you with the resource management).