You don't need to run Classic Shell on Linux.
Classic Shell Doesn't create for any other Desktop Environment than WDM.
You already have "Whisker Menu" for XFCE desktrop Environment.

If you want Xubuntu Linux environment for Windows you can do so just like I did.

The other deep reasonable reasons why some Windows developers didn't ported it to Linux:
1. Some developer use .Net, Directx libraries which are Windows Only libraries:If they've developed from one these: Qt, Java, C, C++, Python, Perl, Ruby without .Net requirements.
They'd already success ported to linux already long ago.
2. Diging down to .Net route there's no going back: Every .net softwares always failed on wine. Except Qt, Java, C, C++, Python, Perl, Ruby they're wine so easily.
I never see any .net, DirectX programmer turn their feet on Linux other than Qt, Java, c, C++, Python, Perl, Ruby Developers.
3. They don't know which installer software they can use for Linux like NSIS, Innosetup:This is the main obstacle don't forget that installer & package manager works different.