Why does Adobe Captivate 2017 run so slow on my iMac?

Same here. It is bad and frustrating. I've found that when you lower your monitor resolution down, it helps tremendously. The lower your screen resolution, the better the performance. But you won't be able to see much of your screen. So, Find your balance. I hope this helps.

Captivate 2017 runs slow and lags on my brand new iMac in the office, running 10.13.6 with 16GB of RAM.  Oddly enough, it runs way faster and smoother on my four year old iMac at home, running 10.11.6, with only 8 GB of RAM.  The only other difference that stands out for me is that at home I have just the iMac display running.  At work, I have two 27-inch widescreen monitors attached to the computer...

Same, but using CP 2019 and it runs EVEN SLOWER than CP 2017. To the point where its becoming unusable.. 

Clearing the cache doesnt help.  but thanks for trying... Ughh.. this is irrating....

When did you clear the cache lately?