Windows 7 and Windows 10 both have pros and cons when it comes to gaming.
From my experience, I've seen that Windows 7 performs very slightly better in games, which is probably due to it being much less bloated than what Windows 10 is. Even though that's the case, there are some things that you have to sacrifice when going, or staying on Windows 7.
One major factor for my switch to Windows 10 again is due to the bugs of having multiple monitors, the biggest bug being that windows, on monitors that aren't primary, won't be updated until an action on that window occurs. Another bug related to the aforementioned one is that often times, windows will be "missing parts" until an action occurs.
The reason why I bring this up is because most people that I know, that game, often has multiple monitors, and that they'd be very discouraged to switch due to these weird bugs.
Another thing you're going to be missing out on is support for the latest games and programs.
Because Windows 10 is the standard, most programs are developed with it in mind. Old OS:es, especially ones that are approaching EOL/are at EOL, gets less and less support for each day that goes, if any at all. Programs and games made in UWP are an example of modern things that'll never be available on something like Windows 7. Not to mention that stuff like driver support will also be dying off.
To sum up, I don't think the switch to Windows 7 is worth it; if you're already on Windows 10. For the average person, I'd just recommend using Windows 10, with all the bloat removed.