But this just solidifies what I said. By the way everything you listed isn't the operating system. What would apply to the operating system would be an upgrade from one OS to the other or major security updates like service packs. It is very possible with software updates for software to ask the machine to do more in the background which slows it down.
As far as the other things you said. we can take a brief look at those. Various things filling up. Well that does make sense but that isn't anything slowing down. That is simply it is harder to find empty space. It is much easier to find free space if you had 90% free instead of 10% free. This isn't a computer issue but overall storage isue. If you buy 10 storage bins at your house and have stuff to put in them if they are 90% full it would likely take you longer to find free space for your items then it would be if they were only 10% full and you could just drop your stuff in them.
Caches on desktop OS's don't fill up generally especially if they are used as volatile storage. They generally just use space on the hard drive.
Internet browser and app corruption is based on usage and generally don't happen without the users loading uneeded applictions that create extra work for the system to do. The browser isn't slower, it is that extra app bar you loaded with some share ware and installed becuase you weren't paying attention.
I am not saying a percieved slow down isn't happening. I am just saying no matter how you look at it, it is extra work the computer is being asked to do, and normally induced by us as users. Ontop of that generally speaking allot of stuff that is creating that extra work and percieved slowdown would likely be reloaded if the device/computer is reloaded.