Launching another browser presents the usual "do you want me to be default" dialog. It's completely trivial to change your browser preference. Yes, I would have preferred if Microsoft had left my browser preferences alone with the upgrade, but this is blown a bit out of proportion.
It's also a bit disingenuous to compare today's situation to the Internet Explorer case that's literally 20 years old. I find it improbable to believe that anyone using Windows 10 is unaware of alternative browsers availability.