On osrs and rs3 you're able to change worlds to avoid content being completely blocked off. Again, every major server recognizes this important detail and creates rules accordingly so new players don't join, get locked out of content by a toxic player, and leave. You're free to believe this is better. But the shrinking player base may disagree. I don't say this to be disrespectful, I say it to give honest feedback. An actual example of a rule would be that on multiple servers, it's considered ragging to kill someone with the express purpose of blocking content from them. If you're killing someone with no risk, and no reward repeatedly, it's rightfully considered ragging. That's a start.
Rewarding unique kills is something nearly every server does. A small reward for killing someone you haven't killed within a certain period of time. Obviously there are IP restrictions on those killing rewards, and rules around abuse.
Also, dying isn't the problem. It's locking people out from content. Dying is a part of the wilderness. It always has been, always will be. But by having one world, you prevent the only form of escape that allows you to engage in content if the person killing you decides they don't want you to do it. That's makes players leave. That's what makes it toxic. Even RS has rules against this, it's lumped under the player harassment rule and they changed major in game content on OSRS because of people locking down content.