@alcinnz also many people have multiple devices (especially if you think family/household units) and increasingly value easy access to the same stuff/content/credentials etc across most of their devices (perhaps shared partially with other members of the family)
So until open source includes good alternatives for phones/tablets/smart watches as well as game consoles/tvs (or boxes connected to them) and laptops/desktops it likely has to coexist with iOS/ipadOS/Appletv or Android and misc TVOSes