Lightroom 2018 CC - Import of photo extremely slow

I experienced the same thing on my PC laptop in late November 2017. It was so slow (approx. 4 seconds per photo) that I bought an iMac thinking it would give me relief from the abysmally slow import process. Nope! Even the iMac is terrible. As it imports the entire folder tree blinks after every single photo download (and this was the same thing that happened on the PC). At the bottom of the hard drive root directory a 'Lightroom' folder now appears briefly and then disappears with each and every photo downloaded. This is new with one of the most recent CC updates and I am convinced it is related to the increased import time. Anyone else noticed the blinking file tree with the new and much worse import process? What used to take a couple of minutes now takes a looong time. We're getting much less efficient work streams, and we need the opposite!

I have the same problem.  Since Upgrading to LIghtroom Classic this program is almost not usable as a professional tool.  I bought a canon 5d mk iv and the imports take 5x - 10x longer than before.

This is really a set back. 

I sent adobe a bug report and heard nothing.

Same here. Abysmal import speed and it doesn't show more than a couple previews until the entire import is complete.

Very slow for me too. Also having issues with the current import not showing thumbnails and files as it imports. Shows a few after a bit of time but requires all files to be imported before I can see most of the images. Seems to really slow everything else in lightroom too and there seems to be a delay in doing other things in LR until import is complete. I've been using LR since version 1 and never have seen this issue with importing before. It really becomes painful when importing many images from something like a time lapse sequence with thousands of images.

Try checking the standard preview size in Catalog Settings, mine changed from 2048px to 3840px.
Also when importing try a new feature - "Embedded and Sidecar previews"