The game is currently very laggy even with mid-high end machines. I built my current rig, 8 core 32gig ram for this game a few years back. It used to run smooth for 400-700 turns regardless of map size. After patch 2.8, no matter what map or ai count I use the game slow down at around turn 100 then runs to a crawl at around turn 200. Its anoyed me so much I have quit playing it untill this is resolved. If you browes the steam forums you will see multiple threads and people all complaining of the same thing, high end machine struggling to run the game smoothly. I doubt it is you machine tbh.

As far as I am aware (from frogboy posts) the game will use all available cores it has access too, I can vouch that this is the case. With this issue mentioned above, when I check what the computer is doing duing this slow down it uses around 40% of my 32 gigs of ram and the cores are sitting at about 50-70%. So I know its not the rig (All other games run sweet as).

All that been said. I am in the process of building a £2000 upto date rig. (Have to buy the parts bit by bit due to finances). I have taken the plunge and got a 2700x for my rig sitting in a Crosshair Hero VII motherboard with water cooling. Its as far as I have got. RAM (3200mhz 32g of), G-Card (RX580 Strix) and SSD's (950's x3) to get. From reviews i have read the gaming performace boost with the new variations of ryzen 7 cpus is minimal for the cost, once past the 1800x. You gain more from higher memory mhz.