https://www.safetydetectives.com/blog/windows-defender-vs-antiviruses-is-defender-enough-for-you/
Windows Defender failed to block many instances of malware during testing. And Microsoft doesn’t issue enough regular updates to the Defender software. And let’s say that you do get a virus, Microsoft isn’t going to help you — they’ll just tell you that you should’ve had another antivirus installed! In general, while Windows Defender is a good basic antivirus, I wouldn’t currently trust it to keep my PC safe, not even running Windows 10.