C# devs can open decade+ old solutions without issues, maybe this is just "normal" for the JavaScript ecosystem, but there absolutely exist other ecosystems which don't absolutely waste your time in this way.
You can open and build a back-end application that targets e.g. netcoreapp2.1 (6 years old target) just fine, it might require installing you an archived SDK for the build to succeed (which you can download regardless, it will complain that it is EOL though) but it's an otherwise simple procedure.
For library code it's even easier - if you have netstandard2.0 target, it will work anywhere from .NET Framework 4.6.1 to the latest version without requiring any maintenance effort whatsoever.
On Windows, Visual Studio will happily work with .NET Framework 3.0 (which is ancient) and more.
I know for sure that I can clone a random project on Github, hit `dotnet build` and usually expect it to work on the first try. The rate of bitrot for average unmaintained JS project cannot be compared. The average dependency graph of a .NET project is going to be 10 times smaller too.
If this isn't enough, there are tools like Yarn which encourage vendoring dependencies to ensure that as long as you have a copy of the repository, the yarn CLI, and a valid version of NodeJS, you can always run the project.
It was open much the same in both. If you're happy using outdated and unsupported components with security issues AND you can get hold of the right version of the dev tools and plugins AND your hiding environment still supports the old platform, you can maintain the old version with minimal change. But should any professional developer do this?
In domains where software is expected to run for years, if not decades, it's common to archive the entire toolset, along with libraries and SDK's in case you need to fix a bug/add a feature 10 years later. Obviously, in this case you can't have dependencies sitting somewhere on a server you don't control.
There are also situations where this is forced by regulation: you need to recreate build xxx.yyy.zzz 7 years after release because a customer reported a serious bug and it needs to be reported to the relevant regulatory agency and investigated.
It's arguable whether this is the correct decision, but it makes things slightly harder than they used to be
For some definition of "without issues"...
Can remember trying to update a Unity project so it'd be still buildable for 64-bit Mac devices. The very first version bump I done resulted in several critical libraries no longer working and there being no clear alternatives to swap in.
This depends highly on what dependencies are in your C# solution.
Same for his node project. If he'd stuck with dependencies that are just plain js - I'd bet money his project would have installed & built just fine.
By the time you're hitting the native addon apis and doing things like compiling python and C/C++ code... you're going to feel all the pains of those ecosystems too.