I understand that some people are just running on old hardware that may be incompatible with Windows 10, although this most likely means they also may not have the resources to run more modern games. And in some cases you have to run Windows 7 for some specialized software that doesn't support 10.
But Windows 10 is a good OS. I find it painful when I have to use Windows 7, because frankly its extremely clunky by todays standards.
I have 3 MAJOR issues with Windows 10, all of which are of Microsoft's creation and could be easily fixed but they refuse to do so.
1) Automatic updating. Look, I'm a big boy, not some tech noob. I have 20 years of experience as a system administrator. I will update my computer when I am ready to update it (after the update has been properly tested out). I am not going to waste my time dealing with rolling back broken hotfixes and not tested enough patches on my own systems. Enterprise editions have the ability to prevent this crap, which is something that should be available to everyone. Sure make the default be that it updates, make it a little difficult to change the behavior so that it isn't something everyone sets, but I refuse to not be in control of anything that is running on my computer. There should be no ability to remotely force an update or installation of software/changes to a computer that you don't own. It is my system, I paid for it, I pay to manage it and keep it operating. I will not sign away my rights as the owner of the system to let some unknown person or entity to make changes to my system (this behavior would normally be considered "hacking" if it was some other entity that changed computer software on another computer system that they did not own and broke something in the process of those changes...)
2) Removal of backwards compatability to some older software. I get it, there comes a point in time that you have to simply say, sorry, we are not supporting this anymore. However, there is a fairly simple fix, which would be to have allowed people who had a Win7 license to be able to both upgrade to Win 10 and still run Win 7 in a VM. But MS doesn't want that and instead wants you to have to buy a separate license for the VM (or really, the Win 10 since you already own the Win 7 license).
3) Spyware/Adware baked into the OS. I don't want to see adds in "tiles" or anywhere else on something that I am paying for. This is a OS, not an advertising platform (yes, I know this also exists in Win 7, but at least there it was not originally baked into the OS, and since I actually have control over patches applied, I can and have kept all the patches and hotfixes that included this off my systems).