Those Macs have very poor graphics cards, and that’s where you’re having the issue, they hadn’t updated the graphics cards for way too long and they weren’t that great in the first place. Macs tend not to have a very good GPU, most of them these days are using the integrated Intel GPU’s. There just aren’t many people that game on Macs which is why they don’t have them. If you want to still develop on Macs then it looks like the iMacs have the best GPU options. The new graphics cards are more suited for 3D work in 3ds Max or Maya, and don’t run well in games while there are actual gaming cards available for the iMac.
You may have an option of being able to upgrade your graphics card, but you would have to do research to find out what graphics cards are compatible with Mac.