“Windows 7 still runs fine on my PC.”
People can do what they wish, but it would take a heck of a lot to get me to replace the operating system on my computers, and I’d be silly to think there won’t be problems.
It’s an even bigger problem if your Windows 7 box gets exploited
I have one of the larger collections of vintage hardware going back to the late 1970s including such greats as the Timex Sinclair 1000, TI 99 4a, various Commodore and Atari computers, the first XT clone that I put together, and even a few rarities such as MSX computers. I have a shamefully large pile of old laptops. I usually used them until their surface mounted chips started coming loose and my attempts to resolder them started to become futile. So, I can identify with your situation.
Trying to upgrade the operating system on your Windows 7 computer would likely just be asking for problems. I used to set up a dual or triple boot setup when upgrading to a new operating system. These days laziness has caused me to just keep numerous operating systems in virtual machines and play with them that way.
There are secure browsers and email programs that still work with Windows 7... that situation is now causing some challenges with Windows XP and the hardware that was designed to run it. It takes a little effort, but even a Commodore 64 can still be used to do a little web browsing.