Overwatch is quite different from Apex Legends. In Overwatch, you only have 2 teams. In apex legends you have 20. Most damage works in overwatch because the only other people who could finish the kill are your teammates, but in BR's you have dozens of other people from different teams that could finish the kill.
Apex Legends is a survival game. Finishing a kill is 100x better than doing damage. It's just like how long range sniping battles are kind of pointless because you can't finish anyone. Doing damage just doesn't really matter. Healing items are super abundant and it's very easy to get back up to full hp. I could do 700 damage to a single guy in a long range battle but it doesn't mean anything. In the end I'v done nothing more than waste a few of my meds, wasted ammo and given away my teams position which will probably lead to use getting quinta partied and killed.
Also, since it's a survival game, downing an enemy is super important regardless of whether you did 100% of the damage or the last 1 dmg. Anytime you down an enemy, you potentially save your teammate and cut down the kill time allowing you to loot and escape faster before the notorious third party comes and wipes your squad.
They can't copy/paste mechanics because the games are fundamentally different. I think last hitting is a very appropriate style of kill rewarding for this style of game. And if you're a consistant player, you should be getting your fair share of kills anyway. If you're really running into the problem where you're constantly getting a very disportionate ratio of dmg/kills then you should probably re-assess your playstyle because it's probably not as effective as you think. I'v seen people argue that damage is a better end-game stat than kills but it just isn't true. This isn't a race for the most dmg. Winning games require strategy and third partying teams to 'steal kills' and wipe the squads is a very effective way to win. All that matters is that the other players die and you're the last team standing.
