Were many gameplay mods created based on the HD SDK? It has been around for quite some time. And only a few mods were created on the ERM platform. Let's talk when at least one is created.
Okay, let's not count HotA. Although homm3.h from the SDK (and other files from the SDK) seems to be common for both the HD mod and HotA (with minor differences).
Then the only mod is the SoD_SP plugin.
https://docs.google.com/document/d/1JlQ6TC97d_Bb1g_sDRpxTvkKHtyXgZ3qORG5LJS8tp8/edit#
The interesting thing is that the patcher appeared, but there are 10 times fewer Heroes players now than when ERM was around. Accordingly, there are 10 times fewer modders.
My skepticism towards all sorts of "intermediary layers" (which people really spent a lot of time creating) arose many years ago. I had to write a thesis, and to solve the problem, I was given MathCAD. I had to realize that the developers simply didn't include the things I needed to solve the problem. Everything was easily solved in Delphi.