Function names like "_dyld_find_protocol_conformance" seem to indicate that DLLs might need to be accessed, and my (entirely subjective) impression is that this general area seems to have become a lot slower in recent macOS versions, at least when system DLLs are involved.

It’s ms, that slow because every protocol conformance in every dylib needs to be checked. When this gets to 100k+ like in many large apps it takes multiple milliseconds