I agree that alignment locking is not the usual for D&D. You don't really want to do that too much because you want players to be able to use the weapons they find.
However, you don't specifically call out that a weapon belongs to a particular god and then not restrict certain people from using it. For example, you would not let Shadowheart use a weapon blessed by Selune because she is a cleric of Shar, Selune's mortal enemy.
I could see Everburn not being alignment locked. Maybe Zalk acquired it from somewhere and it isn't a devil sword. However, The Sword of Justice should be locked so that certain types of people aren't able to use a weapon that is specifically Tyr's - King of Good Gods. Someone like Astarion should likely not be able to use it even if they had the proficiency.
This is part of the reason I want the alignment system implemented. It just doesn't make sense to allow someone of a good alignment to be using something from an evil alignment or vice versa.
You have a fair point about the Sword of Justice only being used by a good aligned character, but I would also add that if you are going to alignment restrict it then not only should it have the abilities it has for good aligned people but a special buff SPECIFICALLY for followers of Tyr...
That said I too would like to see an alignment system in BG3, I'd like to see them adopt the PF:WotR system where you largely start off as neutral and your decisions determine your alignment (with obvious exceptions for Paladins and Clerics who's starting alignment would be effected by the deity they follow)
but that brings up another point... IF Larian did institute an alignment system they would have to some how come up with a story backed reason that oath breaker can still use the sword (like Zariel corrupted it or something, but then they'd have to make an additional quest for you to cleanse it)
