You cannot cut and past even a simple vector shape from the very latest Illustrator CC into the very latest Indesign CC without the shape being turned into a graphic in Indesign. I back installed to the last versions for both programs and it is work again. I have this exact setup at home (Mojave) and it work perfectly but at work (High Sierra) I had upgraded to the latest of both programs and hence the issue.

What should happen is the shape from illustrator remains an editable vector in indesign.

I experienced this today (19 March 2019)