Old HD X New HD
Before anything, i'll try to explain in pratice what changed in gameplay. To do that, let's consider two players: A (aggressor) and B (victim) --> i think their role in our imaginary scenario is self explanatory...
In the old HD, what mattered was what happend in player B's vision, which means that B would only be damaged when he was hit in his vision.
In the new HD, what matters is player A's vision, which means that B is only damaged when A hits B in his(A) vision.
The pratical results of the old HD was not having any response or control over your aim, in other words, having good aim and hitting targets didn't mean anything when the other player was constantly moving. By the other hand the player had control over dodging bullets and escaping from enemy's swords.
The pratical results of the new HD are having almost full control and response to your aim, which means that if you hit your taget, it will actually be hit (almost always). As a tradeoff, you don't have control over dodging bullets and swords, which means sometimes you will be damaged or killed even if in your screen your enemy didn't even touch you or completely missed you.
Why is the new one better?
Even though it seems like a tie from what was stated above, the new HD tradeoff is much less harmful, in pratice since bullets are actually fast, you didn't really have control over dodging bullets anyways, you would just keep on the move to try to be a harder target, the real difference is that it takes more miliseconds now to realize if you dodged them or if you were killed, but you can still dodge anyways. This is still bad, but actually being encouraged to have good aim is much better for the game since it is something you have much more control over and that can reflect actual skill in the game, being therefore, fairer.
Some considerations
Of course it's understandable that the older players (like me!) who mastered the old HD over the years, and were able to use it in their favour, will not like the new HD at first, it's a matter of getting used to it, or better, learning it. I myself got so used to the old one, that i've trained myself over the years to not try aiming directly at the other players at all, because it didn't matter! Just remember everytime you rage about a BS death and blame the new HD, how much BS deaths we've had with old one.
Basically, learn to actually have good aim and hit people, and remember that now people ressurect, so if you 'kill' someone don't relax, you got the kill but they've some miliseconds to hit you before they actually die (just like before, but now there is the weird ressurect animation, get used to it).
The only thing that i would argue was complete ruined by the new HD are swordfights, but they always relied on broken mechanics to be fair, even if i loved them to death, and ruining that to have much better gunfights overall is a worthy tradeoff.
I was raging about how the new netcode had 'ruined' the game too somedays ago, when i first experienced it. But after playing some Slow mo Rocket launcher, CS BNG, and Sniper maps, i learned to appreciate how now your aim matters!.
TL DR: git gud