Fixed it! I recently had to reinstall windows (long story), and when I tried to run Eldritch, it popped up the same error. That made me think the problem was with my new Windows install, and not the game. After a bit of searching online, I found this question from a Windows user with the same error for a different game: https://answers.microsoft.com/en-us/windows/forum/windows_7-files/xinput13dll-is-missing/b6566b88-b8dd-4dd3-abc5-2efac787a93a
The answer was to download the DirectX End-User Runtime, found here: http://www.microsoft.com/en-us/download/details.aspx?id=35
I figured since it comes direct from Microsoft, it's probably safe. After running it, I tried Eldritch and NEON STRUCT, and both worked.
Sorry for the unnecessary post, but I hope it'll maybe help someone else in the future.