I skiped the mid part of your post, where you were talking about your religion believes ... so if there is answer to my question ... this is the reason.
Most cruicial part of the question is missing ... what effect it would have on gameplay?
The mid part was more of a "why I'm creating this post" and "something to think about". In other words, it's my beliefs, and Pathfinder's Lawful Good beliefs don't seem to coincide with mine. So keep that in mind when you are making a decision on this. If Larian was to implement alignment, would you REALLY want it to be dynamic like Pathfinder where the game can shift your alignment because Larian believes your actions aren't being Lawful Good (or whatever alignment you are)? I, personally, find that Owlcat's Lawful Good doesn't align with my own, and that was the point.
As far as what effect to gameplay, it boils down to spells and items mostly - at least from a pure mechanics perspective. In D&D, some spells protect you against Evil or Good or Lawful or Neutral or Chaotic alignments. Some items do likewise or are only usable by specific alignments, making those items more unique and making it so that you can't just use a powerful, holy sword of Tyr when you are a nasty, evil paladin of Zariel (such as with the Tyrite hunting Karlach - assuming he's an evil paladin of Zariel). You want to use the Sword of Justice? You need to be Lawful Good. You can't use Tyr's power against Tyr's own people. Likewise, you can't use Shar's power against a Sharran if you are a Selunite.
That is the point of alignment from a mechanics perspective. The other point is that it is supposed to help you get into the role of your character. If you select an alignment for your character, it helps you get into your character. If I know my character is Lawful Evil, I will try to play my character as a law abiding nutjob who obeys the letter of the law regardless of how cruel and harsh it is. It helps me make decisions in dialogue because I have a more firm idea of who my character is.
As BG3 is now, I can quickly create a character and then have no real clue what kind of personality I want to give them. So, what results is a rather chaotic approach until I get a feel for how I really want them to be. At least by choosing an alignment, I'd have a more firm idea. My Rogue is Chaotic Good, so I know that when it comes to dealing with Us, she's probably going to not kill it because she tries to not harm any creatures, even if they are potentially evil. My Chaotic Evil Drow Sorcerer would likely try to keep Us alive and cripple it so that it can use Us as a minion for as long as possible. My Lawful Good Paladin would probably be more black and white, seeing Us as an evil creature that will undoubtedly kill others if he doesn't kill it immediately.
Without alignment, I have had several playthroughs with characters where I got to Us (as just an example) and said, "What am I going to have this character be? Hmmm. I don't know. Should I be Chaotic Good? Should I be Lawful Good? Should I be Neutral?" And then, for Us, I chose to be Chaotic Good but later wound up floundering a bit and being Lawful Good. Then later I chose to be almost borderline Lawful Evil all because I didn't really have a firm idea from the beginning what basic personality type and alignment my character had.
It's not REALLY vital for story and roleplaying to have an alignment, but it helps. So, I'm not saying that it's imperative. I'm just giving you an idea of how it could help players in the game.
