XP was popular.
Vista was very unpopular and most refused to upgrade.
Win 7 was & still is popular, as many large corporations still use this OS.
Win 8/8.1 switched from menus to tiles which was very different so many people found it difficult to transition and many even downgraded to 7. It was not a huge failure like Vista because some people like the tiles, but it also was not as successful as Microsoft had hoped.
Windows 10 learned from the mistakes of 8 and offered both the tiles & the menu plus it was available free for about a year to encourage people to switch.
The truth is you will likely use the OS that came on the computer you buy. If your old computer with Win 7 breaks then if you stick with a Microsoft OS then your new computer will likely be one designed for Win 10. If you buy a computer designed for Win 10, it is unlikely you will even get it to function 100% if you try to install an older Windows OS. Manufacturers have an incentive to write drivers to work with the current OS that will be shipped with their hardware; they have much less incentive to pay programmers to write software for older OSes and there are just so many drivers to make all the pieces communicate that you invariably find some tiny piece(s) that will not function on the older OS.
The good news is that within a couple months of using Win10 you will hardly remember what things are missing.
So has it gone downhill? I don't believe it has; it has simply changed. Most of us resist change, some embrace it, but it will come either way.