How exactly does it match the definition of a scam? Windows does get viruses, and it does protect against them. It's not something you actually need, like most consumer VPNs, but they have high pressure sales tactics to trick people into buying it, but they do deliver what is promised, which makes it not a scam. They are creating artificial demand with their scare mongering, and I tell everyone I know not to get it, and to enable Windows Defender, but that's still not a scam.

It depends on your definition of scam. Is McAfee a total fraud, not delivering on its core functionality of anti-virus scanning? No. But it's selling something most people don't need and uses information asymmetry, fear, and dark patterns to make money. Microsoft Defender has solved the anti-virus problem. (It doesn't solve the computer security problem but that's out of scope of AV). To play devil's advocate, without bundled bloatware PCs might cost $10 more.

They push this message hard: unless you pay us, the bad guys will eat your lunch.

The truth is that if you uninstall their software (and hopefully also if you just let the trial lapse, though I don’t actually know whether Defender Antivirus gets enabled automatically in that case) Microsoft will defend you against the lunch-eating bad guys just as well as McAfee, for free.

That easily qualifies it as fraud.

For that reason, I’m willing to call it a scam when preinstalled or otherwise installed without user intent. I wouldn’t call it a scam if people installed it deliberately (though I would still disparage it and its tactics).