Itch does have scanners.
The problem is, that the malware uploaded on Itch often does not even trigger on virustotal and they scan with about 70 different scanners. Meanwhile lots and lots of games do trigger there with false positives.
But a good scanner on your system will do other things to protect you.
Unfortunately, a common threat of the malware is things like cookie theft. A software does not need to do many virus like things for that. Read files, upload to internet. It's a Windows design flaw.
What does protect against this type of attack is using a sandbox. Curiously enough, the Itch app provides one. https://itch.io/docs/itch/using/sandbox.html
I guess it was just too easy to implement, so they just added the feature. You can do this by hand too, without the app. Just create a user like they do, that does not have rights to view other user's files. If you shift-right-click an exe you get the option to run the exe as a different user. You need to enter that username and password and then the app will not be able to steal the cookies of your main users's browser. And those cookies would be your access to logged in accounts.
Will not protect against system exploits and such, but hopefully those get caught in one of the scanners.
Ultimately, Itch needs to change something fundamentally. It is just too easy to upload malware. And it is trivial to upload malware that bypasses scanners. Just try differently till it works. The criminals do not upload 1 game a year, they upload 10000+ malware per year.