Windows Defender Vulnerabilities?

Not that I'm defending Defender "see what I did there " , but to my knowledge, none of the standalone AV's are completely effective at stopping true Zero-Day malware, they simply can not push the signatures out quick enough. WD is much better now then it has ever been, that said I recently stopped using it again, not because I fear it will not help protect the system combined with the rest of windows built in security, but because WD is rather Hard on the Hard Drive "did it again, just cant help myself"... lol