1. entity framework core code first does not support table per type inheritance, which makes database migration necessary
2. some libraries do not support .NET Core yet
These APIs are almost entirely coming from .NET Standard 2.0. See the jump in APIs in this table[1].
We often get asked if this is going against the promise of a light-weight development platform. Answer: not really. The new APIs are not being added to a single library, but several, including new ones. We will be updating our publishing tools to make it easier publish apps w/only the libraries you need. We are also looking at going one step further, which is publishing only the IL you need (intra-assembly optimization).
I am spending the week presenting at two Microsoft conferences in Europe (Milan, Amsterdam). I heard very similar feedback on EF yesterday in Milan. I will be passing this off to the EF team.
FYI: I'm a .NET Core team member.
[1] https://github.com/dotnet/standard/blob/master/docs/faq.md#i....