It's not as big a deal as you think because most banking hacks are done via browser vulnerabilities rather than OS vulnerabilities. The exception being if you've somehow managed to install a keylogger, in which case the issue is the user and a decent AV should detect and block the keylogger.
As long as you use a browser that gets the latest updates (Firefox, Vivaldi, Chrome), run a decent AV, and don't install dodgy software you downloaded from some dodgy site, you should be ok.
AV is definitely not snake oil. I worked in Enterprise IT and a robust AV alongside other security measures is a must and does catch alot. More than the built in Windows security catches. Plus the AV normally incorporates a virus/malware removal tool which tends to be better than Windows built in tool.