Is the lack of notarization truly an issue? Aside from demonstrating that the creator has a paid subscription to the developer program, what does notarization accomplish that isn't already handled by XProtect (i.e. a YARA scan) and the Malware Removal Tool (MRT)?

Are there any examples anywhere of malware that has slipped through the client-side XProtect pre-flight checks, but that the server-side notarization checks have caught? Most independent macOS security literature I've read implies that notarization and code-signing is more about retaining centralized control of the app distribution process, but does not actually contribute anything to the malware mitigation tools that have been built into macOS for a very long time.