Okay then.

I don't disagree with you, what you're saying is true, but grandma and grandpa probably don't care, they just want to watch cat videos on YouTube. I understand your insistence on an upgrade and yes, it would be beneficial, however in this use case I would probably advocate for Chrome OS or something simple like Mint that will not overburden the old hardware (easy on the laptop) and will not involve a massive change of UI (easy on grandpa and grandma). The tl;dr is that you're not wrong, but you're taking this back asswards. Your solutions need to be tailored to the user to maximise utility, something you'll learn over the course of your career if you ever choose to monetise your skills. Again, XP is serviceable, albeit not recommended, for this use case besides high risk activities. I certainly wouldn't put my CC information or private details on a machine like that, but would I browse YouTube on it? Probably, because it just doesn't matter. And no, you're certainly not more knowledgeable, but you can think that if it lets you sleep at night.