I'm also very surprised you'd claim that not all Microsoft shops are buying into dotnet core - I've seen the very opposite; every client I've worked with has known dotnet framework has been superceded by core, and has been eager to move. A decent portion of this is driven by certain containerisation, which (realistically) means dotnet on Linux.
The only real limitation with dotnet core has been the lack of managed C++ support - a niche use case, and only relevant on Windows, but even this has been resolved in dotnet core 3.1.
Considering the not insubstantial performance improvements in dotnet core, and of course the benefit of cross-platform code, I'm really interested to hear about the limitations of dotnet core you've found (the switch for me and all the enterprise clients I've worked with has been great)?