I don't disagree agree that that's technically true. But in practice it's simply not going to happen. My 70 year old mother just wants to use outlook to mail her friends and I've setup het phone to save the pictures she takes of her grandkids (my nieces and nephews) on OneDrive so she can share them easily with the rest of the family. Same thing for my brother and my SiL. For 80 euros a year I get a full groupware experience with no extra work. Is it perfect? Of course not. But even with a higher budget there's no feature for feature alternative.

Hell, the chances of getting my work to switch to OSS cloud subscriptions is higher than getting my family to do it.