It’s highly unsafe. Vulnerable, full of bugs. The worst OS ever created.
While that may be the incessant public relations drumbeat of Microsoft in an ongoing attempt to support the fallacy that the latest version of Windows is "the most secure Windows ever", the malware and virus statistics clearly show otherwise.
Consider that the download size of a single Windows 10 update may be larger than a year's worth of Vista updates back in the day and may take significant fractions of an hour to install. I remember contemplating Windows 7 updates in terms of how many Windows 95 distributions they were in size (Windows 95 was available on 13 floppy disks; about 19MB).
30 years ago, "zero-day" meant that someone had cracked the copy protection on a game or software application within two dozen hours. Today it often means that Windows has a new vulnerability
that has been discovered within hours of its release -- something that the programmers and pre-release testers at several levels weren't able to identify.
Windows Vista doesn't present the attractive "threat surface" that Windows 10 and 11 share (though it is
vulnerable to the bugs in Windows 11 that remain from Windows Vista and sometimes earlier). Windows Vista wasn't perfect by any stretch of the imagination but it wasn't any more flea-bitten than Windows 11.
The worst Windows OS ever created was surely not Vista. It would have to push aside at least two other major clankers in the form of Windows Me (an attempted bridge between 16 and 32-bit Windows) and Windows 8 (an attempt to change the direction of Windows that was substantially rolled back With Windows 10).
If it doesn't cause anyone else heartburn and hasn't been trashed thus far, why not?