As i see it, Paladins don't need a deity, but every character should have the option to follow a deity, like you have in Pathfinder games.
Paladin abilities in the 5e manuals (supplements included) talks about showing your holy symbol to execute abilities for most subclasses. The holy symbol is non-optional in the starter equipment in the PHB. The class description mention using divine powers (Channel Divinity, Divine Sense, Divine Smite, Divine Health) and swearing your oath to an higher power to fulfill some holy quest. It even give a list of gods your paladin could follow.
Reading the PHB class description, I do not have the impression that WoTC wanted most Paladins to not follow a god/swear their oaths to one. Also, it pretty much says they are supposed to be good aligned and act as a tool against the force of evil (as defined by alignments). WoTC wrote Paladin as if they were still in an edition pre-5e. Oathbreaker even has "any evil" as alignment restriction in the DMG.
As a result, the lack of god selection and no alignment in BG3 is causing issues for Paladins. Larian had to go strict with the oath tenets/code of conduct (no live GM to customize to the player's wish, no gods to change the pov of them) and Oathbreaking doesn't have an evil alignment requirement, which means it is available right away after breaking once even if it was for kicking someone evil.
