Meh, the reason many people weren't targeting .Net Core until recently was because of the huge pain in the ass it involved. .Net Standard 1.0/1.1 were missing a LOT of API surface area that many libraries needed. .Net Standard 2.0 fixes this, and makes life easier for library authors who already support multiple runtimes in the process by providing a sane upgrade path from the hell that is PCL's. It's all about tooling, there's no reason for library authors to not target .Net Standard in their projects now unless they really need some Windows/Full-specific assembly that isn't included.
> Meh, the reason many people weren't targeting .Net Core until recently was because of the huge pain in the ass it involved
+1000. It wasn't even library support, it was the tooling that was a huge pain in the ass. Half the time it didn't work right, builds broke unexpectedly, build file formats kept changing, cripes what a pain. I swore off it until the early .NET 2.0 standard prereleases when things seemed more stable, and it's been much easier to port my libraries.