Update: VisualStudio twitter account responded to me to note that this is a bug and they are working on a fix for the future on this….
I have two responses to my post:
1) The using issue noted with things greyed out was actually a ReSharper issue. If you upgrade to VS 2017 15.3 and use R# make sure you update it as well to 2017.2.
2) The Yellow triangles issue is being looked at by the Visual Studio team but honestly I believe it to be linked to warnings in the build that those references are being coerced to either lower dependencies (ie Newtonsoft at different levels) or previews. The quickly evolving .NET 2.0 world may have exacerbated this issue. Yellow triangles have traditionally meant missing but check your warnings to see if that is related and then review the dependency chain. I will update this answer once I hear back from VS team (shout out to them and Damian Edwards + Scott Hanselman for helping me with this on Twitter).