This may be a silly question, but as far as online games that work, it shouldn't matter if my friends are on Windows, right?
For the most part it's fine like the other comment mentioned.
However there are a few edge cases like Borderlands 2 that is like pulling teeth to make work.
Since a great deal of essential services rely on the Internet. It would probably be a bit like New York during 9/11 or Canada when one of their biggest ISP died.
https://en.wikipedia.org/wiki/Communication_during_the_September_11_attacks
https://www.ctvnews.ca/business/what-we-know-about-the-network-system-failure-that-led-to-the-rogers-outage-1.5982790