The thing is, even if you install a third-party antivirus, Windows Defender isn't fully disabled and will continue to run in the background to some extent. It's fully integrated into the Windows 10 OS. When it detects a third-party antivirus, it turns off its real-time protection, but it still runs in the background.
Also, the majority of antivirus issues with Media Center are with third-party antiviruses, like Bitdefender especially in the past. With Windows Defender it *can* cause issues (especially when a brand new major MC version is released) but otherwise it can be tamed pretty easily, and once tamed it doesn't really cause issues after that.
Also, Windows Defender is as good, if not better than most third-party antivirus applications according to third-party testing organizations. While once upon a time Windows Defender was considered a joke, Microsoft has done a good job improving it to the point where it's considered top-tier now. While people can purchase and use third-party antivirus/antimalware applications, these days there's really no need to as Windows Defender should be more than enough when it comes to antivirus/antimalware. Finally, it's built within Windows 10 itself, so it's overhead should be lower than most third-party antivirus applications.
And that's not going into the other part of Windows Defender, the Windows Defender Firewall.