It's way too reliant on their cloud infrastructure though, causing it to detect and react to malware slower than other solutions and it turns to shit the second the network disconnects.
The PC security channel on YouTube has some good analysis of it.
To be honest, for most users, if they're not on the Internet; it's not that big of a deal for their antivirus to be less effective. Most threats come from being dumb on the web.
That thing literally saved Windows, as most users would otherwise have had to install shitty freeware like Avast or pay for premium antivirus solutions, basically paying to try to close loopholes that Microsoft made in the first place.
I almost opted to move my parents to use Linux instead of Windows because of how much time I was spending on fixing the malware and viruses they'd get. Then enter Windows Defender.
Now all I have to deal with is when they get the occasional scam call... "Yes, it's Bob from Microsoft, you need to wire us $900 to fix a virus."
You laugh but windows defender is awesome. People give windows shit but the reason it's attacked the most is because of it's market share being above and beyond leaps and bounds sun vs tiny fleck of dust in space os market shares that Linux and Mac os have. No one's wasting time hacking the tiny stuff as much just because its a numbers game. Guarenfuckingtee you if Linux was number one market share OS it would be getting attacked way more often than any other OS as well. Dont kid yourselves.
macOS and Linux have additional security features at a system level, on Linux most software comes through controlled repositories or sandboxed flatpaks. There are also tons of multi million dollar companies that constantly try to find and fix kernel level vulnerabilities and a distro like Debian, which is very popular for servers, has had less major vulnerabilities than windows 7 throughout its entire lifecycle and Debian exists for other 30 years. So I’d say Linux is would have a few less (different) attacks
Windows NT 3.5 and later NT 4 had C2 security certifications - assuming the system was not connected to a network, and didn't have floppy drives (this was before USB was a thing).
Yeah it literally pops a screen sized warning when anything tries to run as admin.
Linux is very vulnerable as well. Hackers are just really good at what they do.