"Features that are not present or supported by the current generator/plugins combination"

When attempting to load one of my workspaces in 2024.1, I am met with this error:

https://imgur.com/a/wADATSV

The workspace was last loaded in 2023.4, with the Forge for 1.20.1 mod generator and either no loaded plugins or just Nerdy's Geckolib Plugin, I don't remember which. The current combination is the same, 1.20.1 with Nerdy's Geckolib Plugin. Does anyone know what is going on here? Did I do something wrong? Nether Update Expanded loaded fine when I opened it, it's just this workspace causing issues:

https://imgur.com/AT3POwJ