Yeah, most people are like that. One of my brothers is still using a desktop rig I bought new in 2007. All he does is surf and it is still good for that. His son is using one I built up out of spare parts I had laying around. My wife is still using her 10 year old Mac and I gave her a new laptop for Christmas because her 9 year old one was dying.
No, you misundersand me. I'm actually using my computer for real and heavy work -- graphics processing, design, video editing, audio recording and editing, 3D modeling and rendering, book writing, office suite, programming, web app rendering -- all in a professional capacity, producing industry standards level, high quality work.
But games are evolving and my hardware has to keep up with them. When I first got the FX running the games I played then only pushed it to 40-50% loads and all was well. Then came the next generation and suddenly loads were in the 80-90% range. Ryzen got the loads down to the 40-50% range again. Not so with the GPU though. Because the data miners have inflated prices I'm now 2-3 generations behind and this gpu is always at 100%, but I just can't force meself to pay $900 for a $300 gpu. I'm saving me pennies for the day sanity returns.
Yes, while you technically can game on Linux (on a popular distro like Ubuntu), most Linux users will tell you that Windows is much better suited for gaming purposes, simply because most (well-optimised) PC games are specifically developed with it in mind, and most new games are following the latest largest userbase for a PC OS -- in order to maximise their sales.
Personally, I don't mix work and gaming. I made that choice a long time ago. I used to dual-boot Windows and Linux. Now I have one "PC Xbox" -- a powerful Windows computer that I hooked up to my television specifically for gaming, and a AU $400 laptop for work -- believe it or not, because Linux makes it possible to get that kind of work performance out of what is essentially a low-end machine! The laptop I bought was specifically notorious for being slow with Windows 10, with most purchasers returning it to store because they "couldn't use the Internet fast with it".

Now I'm using it to produce professional calibre work, including 3D models and movies.
So there you go -- this personal testimony says something about the power of Linux as an OS.
Since all I do is OC and game I'm stuck with windows. Most OCers reinstall the OS 2-6 times a year due to data corruption but to show how stable my systems are I keep the same install year after year. My system is more thoroughly tested and more stable than stock systems. As for OS slowdown mine has all the usual bloatware that accumulates over time and testing shows a 2-3% difference between it and a new clean install. That's 1-2 fps in games and no one can notice that.
I've actually found that when used just for installing and playing games, Windows does its job fairly well, too -- so I am more than happy to fully concur with this! There is a bit of a slow-down over time as you install more and more games -- as you say -- and the computer -- of course -- needs a reboot every now and then to clear the memory, but overall it plays like a solid machine, and it continues playing for a long time.

(That is as long as you don't keep updating Windows with Microsoft's patches.)
(I was mostly talking about using Windows for work, which is a whole different game...

)
I haven't tried Ubuntu in maybe 3-4 years and that version involved waaay too much typing. I'm a 2 finger hunt and peck typist so it just didn't work for me. Too much like windows 3.1. Would you believe it took me 20 minutes to type this out?
Don't worry, I'm slow at typing, too, and I have to re-edit a gazillion times to make my point across -- what I really wanted to say...

(It sometimes takes me literally hours...)