I am on an older Intel based Mac (2020 iMac to be specific). And I do remember this setup working a while back so maybe it was a macOS upgrade that broke it. I last played Stardew Valley maybe 1.5 years ago so something since then has made my controller stop working.
Thanks for the link. Although it looks like it's for controllers working with Steam in general, instead of for this game only which I'm having trouble with. My controller works fine outside of Stardew Valley and I was able to control Steam's big picture with it. I'll read through it though, thanks!