Re: manufacturers are to blame 100%
It's not just the computer. It's the TV, printer, that streaming box you purchased a couple of years ago and a bunch of other network connected kit that appears to be running Android or BusyBox.
The manufacturers customise the software, do a couple of updates during the first 18 months to fix the most shocking bugs and, perhaps, introduce a few new features. Then that's it. Support is finished and the world rolls on.
I'm not sure what the answer is, I did wonder if manufacturers should be forced to open source their code/build environment for each device as it gets to the end of its support life...