If it's a known problem then eh maybe not much that can be done. What has Avid told you? Why is this specific to iZotope Insight? Can you find a different meter plugin (I know *nothing* about Netflix metering needs)?
Are you able to freeze/commit tracks to help here?
But Ok one suggestion I have is to explore the graphics issues and test Mojave. Other users have reported high CPU burn with graphics on screen here and had it solved by moving to Mojave. But that was with the mix Window graphics not a plugin. Since your XFX card is 580 based I hope it will support Metal and Mojave. See this thread,
http://duc.avid.com/showthread.php?t=404737, James Welch did a great job getting his system sorted out. You could also do a quick check if moving the mix window off screen further significantly lowers CPU use like James was seeing. At least one other user here I think saw similar problems.
I would use that same opportunity to do a full clean install. Not sure what exact drives you have now I would either grab another SSD and SATA PCIe card or just connect it to a spare motherboard SATA II port... good enough for a test. Download the Mojave installer to your current boot drive, run it and select the option to do a clean install on the new drive or spare partition. Then do a clean 2019.5 install and ILM and drivers and just iZotope Insight and test.
I'd test that before thinking about hardware upgrades.
Other random sanity check things:
Ignore errors unchecked
Make sure the payback IO Buffer is set as large as it can be
Double check all optimization (WiFi and Bluetooth off etc.)
Disk cache set to a size (several GB) and watch the disk cache meter to see the session load all into memory (meter turns green).
Try dynamic plugin processing off or on, to see if it improves things.
If you remove all other third party plugins except Insight does anything run better?
... just looking for anything that will lower chance of -9173 errors, these won't affect the CPU burn/graphics problem here.