Why are you not using Windows 10 anyway? there is nothing wrong with it, it's a fine operating system. Never looked back since getting it.
Largely due to Windows update behaviour which is completely broken for my use - I simply have way too many things going on that absolutely can't co-exist with the OS being able to executively reboot whenever it feels like it and/or the disruption from CPU and disc IO it will randomly use when prepping for the next update, etc.
I also find it ugly as **** - I often have Windows 10 up on one monitor (as unfortunately some of my newer systems are only supported on 10 by drivers) and 7 on my main monitor and 10 rapidly become an eyesore while 7 is far more aesthetically pleasing and so less fatiguing.
While less game breaking I also dislike how many features in 10 fall far short of their potential often help back by silly reasons for instance the new start menu could be a really great improvement over the traditional one in 7, etc. but where is the group management? where is the ability to properly customise tiles? where is the ability to scale it dynamically anywhere between a really simple menu and a more complex system? (as required depending on the device you are using and tasks you are doing, etc.).
I also don't find 10 as reliable as 7 for many things - my 10 installs will randomly get periods of stuttering or explorer suddenly deciding it isn't playing ball either until I reboot or sometimes until I reinstall or the start menu will randomly decide to stop responding, etc. it doesn't happen all the time and/or on every system but occurs far more often than it should.