My apologies for the delayed response, work has been a bit crazy.
Anyways, there was a comment about how, with Java 16 being used with Minecraft 1.17 (instead of Java 8), it broke reflection. Which I assume is what Forge uses to patch itself in at runtime (examining Minecraft's Java classes and adding the necessary infrastructure for mods to work). I'm curious to know the technical details of how they're working around that problem as I enjoy low-level technical work like that.