Normal people can definitely install an OS. Last weekend I set aside time help a friend install CachyOS. They'd never used a terminal before and wanted some help.
When I called them, they had already set it up and was playing Risk of Rain 2. They started streaming for me on the Discord Flatpak they installed from the app store.
I don’t disagree that installing windows/macos and certain Linux distros can be stupid easy but to a layman it’s daunting.
In my experience most people who use a computing device may be able to tell me “this is window” or “this is Mac” by virtue of the branding being all over the stuff but for all intents and purposes these things are appliances.
In the same way most people except ambitious DIYers don’t rip apart their 500-1000 dollar washing machine to replace a worn belt the call a repair guy. Or in your case, have a buddy who knows how to do it.
Define normal. I would argue at least 75% of the US population has zero interest in learning how to install a new OS, let alone actually do so themselves.
I say this as a decades-long Linux user (who has tried to evangelize it many times).