I think one can run XP or even Windows 9x if careful (pray and press), avoid all gambling, porn, game sites and use a antimalware host file, and keep an eye on what is running, but with the load that the Internet places on a system today then the PC itself cannot handle much.
Refurbished Windows 10 and used desktops and laptops are cheap though.
Well, I am in an interesting situation, in that my ISP is HughesNet. I think they must run their system like a giant VPN, because I never see any of the "pinging" from Chinese (and .gov) sources that used to see before. (And if you try to geolocate my IP, it tells you it's in Kansas, 1000 miles from my actual.) I don't go anywhere near porn or music sites, don't even view videos. I do not do any banking online. I do not use Paypal, (which was the source of the last two credit card breaches I had, according to the bank. Those were in 2016, and I haven't had one since.) My email provider is ProtonMail. (I wish that family members would not use Gmail and Yahoo, though.) I do not use WiFi.
Because my Part B insurer won't compile their site to run on XP & FF-52, I was forced to buy a Win 10 machine to manage my online prescriptions. It scares me. I had to give up a bunch of personal info to Microsoft just to get the O/S to start up. I've caught Brave storing my credit card info without asking me. Win10 regularly demands that I back up to Microsoft's cloud. I had forgotten what a PITA the updates from Microsoft can be. Too often this Win10 machine literally will not shut itself down for up to half an hour, unless I pull the power cord and yank the battery.
Lastly, I still use some legacy software almost daily that simply doesn't work properly on Win 10. I'm old enough that I once had to learn UNIX for work, but at 79 I'm fed up with being forced to learn new operating systems. So AFAIC I'm keeping my XP machine front and center until they carry me out in a body bag. /rant