Honestly, treating 'Evil' as just self-interested to the point of being willing to place your own desires above the wellbeing of others is actually one of my favourite takes on it, because
A) It makes it legitimately challenging but also very rewarding to be Good (I mean, what NPC isn't going to like someone that actually successfully respects their wishes and needs when helping them?)
B) It opens up Evil as a legitimate option for party members that isn't an instant dealbreaker
C) It allows you to run creatures meant to be 'inherently evil' (devils and chromatic dragons in particular) as assholes but not completely unthinking and unreasonable, which makes them a LOT scarier- these are intelligent creatures that should be just as witty and dangerous to hold a conversation with as they are to fight. A dragon that's undeniably a selfish bastard but can make compelling cases to try and out-RP the players and get them to fall into traps or hesitate to fight them, or a Devil that knows just how to play the role of a corruptor, someone who tempts the party and plays to win the big game.
Yeah. Unpopular opinion, I know, but I really like alignment. It's pretty easy to say "puts self above others" = evil and "puts others before self" = good.
My quick version of law v chaos is "puts societal structure above individual freedom" = law and "puts individual freedom above societal structure".
Feels like a framework closer to how people actually behave and doesn't invite in-party conflict.
Yeah I generally run any non-neutral alignment as "Willing to go out of your way to perform acts of [help/harm], with the alignment being determined by why you did it and whether you feel satisfied by the outcome, and you intentionally do those acts in a [principled/unpredictable] manner."
As a result, most creatures are generally neutral - They may lean in one direction or the other, but a paladin's divine sense will only reveal evil if someone would actively make choices to harm others, feeling no remorse. Any good deeds are an extension of selfishness, done for the purpose of some kind of gain (lawful: gain is calculated or for an existing purpose, chaotic: gain is for whatever they wanted at the time)
A good alignment for a paladin sense means you're willing to make active choices to sacrifice things important to you (or perhaps for your survival) for the purpose of helping others. That can be as simple as giving up something you wanted or as heavy as charging into a burning building to rescue the occupants. (Lawful: does it because it's the right thing to do, chaotic: does it because it felt right at the time)
I disagree with that interpretation. Evil shouldn't be going out of your way to cause harm, it should be willingly causing harm to get your way. The harm is the method, not the goal.
Like, a good person driving down the road will swerve and crash their car to avoid hitting a dog. A neutral person would stop the car and see if they can move the dog, or at least drive around it. An evil person wouldn't even slow down. Why should they have to be a minute late because some idiot dog decided to stand in the wrong place?
Meanwhile, if the evil person swerved and crashed their car to hit a dog who wasn't even on the road, their car would be wrecked and their journey would be totally ruined. They'd be just as foolish as the good person. If you're going to have your actions bound by the same restrictive moral guidelines as good people in a new coat of paint, you might as well be good.
You've got some fair points, and in agree with you - I was just still waking up when I wrote my original comment and misrepresented what I meant a bit. Will edit and update my comment later.