Why does the supposed junk mail feature of Apple Mail only capture legitimate mail?

This is an ongoing frustration. The junk mail feature of Apple Mail seemingly does nothing but capture legitimate mail. Actual junk lands freely in the inbox while at least several times a week I’ll find legitimate mail in the junk folder. How does this tool even work? I’ve disabled junk mail filtering on my Mac, yet that hasn’t helped. I’ve looked at the mail settings on iCloud web, and aside from filters I’ve set, I see nothing configurable there regarding junk handling. And I don’t see any options in iOS or iPadOS.

This feature needs massive improvement. And it needs to have obvious configuration options.