I'm using iMac19,1... and just before switching to OpenCore, I removed all the Hackintosh kexts from /L/E. I've been running that way since OC 0.5.9 and my system has been solid.
I tried that, but ran into the same result. No keyboard, mouse, bluetooth, etc.
Since I'm using iMac19,1 it sounds like it shouldn't be an issue using the older USBInjectAll.
OH, and I should note that the newer USBInjectAll works perfectly when I boot into Catalina. Although I don't use Catalina much, it's handy to test scenarios like this. I expect there will be more incompatibilities/oddities/headaches as Mojave gets older and older. (At some point all my apps will be 64bit and this madness can end!)