I'm Dr. Igor Prosanov and currently I'm just investigating similar effect for carbonacious and hybrid materials. Therefore, your findings about similarity of Raman spectra of different 2D materials are interesting for me. So, I would be grateful to you for more detailed information about these systems.
My answer is that Raman peaks you observing reflect density of vibrational (accoustical) states in your materials but not specific molecular vibrations. This is a kind of SERS (Surface Enhanced Raman Scattering) effect which occures in highly anisotropic systems - self-SERS.
I also have the same binding energy peaks in XPS data in the case of MoS2 and VS2. What are the reasons behind the same binding energy. On the other hand we get the almost same Raman peaks.