It being subjective can also be seen this way: say the game writer says killing A is good and saving them is bad, but who determines that from a moral point of view? It's like political aligment, both sides think they're right and the other is wrong.
Sure. And in real life people who never talk about politics are kinda boring.
Say I plan playing my character mostly as good (as in: trying to protect the less fortunate and go against the bandits), but there is a moment in the game where in my opinion saving that 1 bandit who is trying to improve their life is the good thing to do, but the commoners demand they're punished or banished and then the option to save them and give them another chance is scripted by the developer as evil, I don't wanna be locked out of that as a mostly "intended as" lawful good character.
Sounds like a bad developer and I think the right thing to do if find the forums and make it clear that's a bad choice. I doubt you would find many fans disagreeing with you on this instance. Examples of alignment done badly don't mean all examples are bad.
And it's possible to have alternative alignment outcomes but they should be done in accordance to the Forgotten Realms lore. Should you kill the bandit? If you worship Tyr the question should come down to is this a lawful killing or vigilantism? If it's Meilekki it's a matter of frontier justice. Eldath would say no, all killing is wrong. So if a court has convicted the man the paladin of Tyr has to agree with the court where Eldath or Meilekki would be okay with redemption.
And for every example of where alignment has been done badly there is a counter example where lack of alignment has made the setting shallow.
I loved DOS2 -- making the world burn while standing a pool of blood was good, tactical fun. But from a role play perspective it was pretty thin soup and that was due, in part, to the absence of an alignment system.