The thing is that the better players have an influence on casuals, even if its unintended.
Covenants won’t affect the basic, entry level content. Just like in BFA where Azerite, Essences, and Corruptions don’t have to be Mythic quality in order to beat Normal N’Zoth or get their +15 Key.
It helps to be optimized, but you can be sub-optimal.
That’s why I encourage casual players to pick the Covenant that is aesthetically pleasing over ability choice, even though they’ll probably look up IcyVeins instead.