Wow I hope you're not doing your banking on that PC.

Looking at the CVE for windows 7 after January 2020 (end of support)

https://www.cvedetails.com/product/17153/Microsoft-Windows-7.html?vendor_id=26

Doesn't look pretty. Many exploits to give attackers elevation of privileges (administrator to your PC), remote code execution etc.

These don't require you to download "dodgy" software. It happens because parts of the windows source code isn't coded to perfection (as with all software) and then the attackers exploit the code in a way not originally intended by Microsoft.

This risk is elevated when the operating system is out of support because different windows systems share the same code base, so when Microsoft releases security updates and CVE reports to the internet, attackers can read these and find out how to attack unpatched systems even if they did not know about the exploit beforehand.

So it's imperative to apply the patches in a timely manner usually within 24-48 hours after release.

On a side note windows 7 isn't out of support, Microsoft is still releasing patches for it along with XP. Many enterprises have to use these operating systems for compatibility with their software, they are getting the updates because they're paying Microsoft millions of dollars for them. So are you saying that other users of windows 7 are wasting their millions of dollars for "overrated" security updates?