Societies have inertia. Without a force for change, they will not change. Maybe they would tend towards communism but it would be incredibly slow. Most people resist change and the amount of change required to shift even just a single state in the US from where it is at now to communism would be immense.

The amount of effort and required learning would deter many people and if you’ve removed the racketeering of the bourgeoisie, then they’ve you’ve lost the stick and don’t have a carrot.

Killing billionaires won’t undo the decades of “communism bad” and it doesn’t specifically bolster communism either. Hell, if you made people aware that you were killing billionaires to support communism you’d deter more people because “it’s just wrong to kill people”

Furthermore le petite bourgeoisie commit much less obvious sins in the eyes of the masses, but still support and defend capitalism. As billionaires fall, that class becomes larger. You’ll likely end up killing all the way down to small business owners before you’d reach the communist future you desire, and you’d have become the enemy of almost everyone left alive well before then.

You’re also making the same error as Light if you rely on people “getting the plot.” You are building a system that only works while you’re there to provide the threat. It will not last and it will fall to pieces again as soon as you’re gone.

Trees that never dealt with wind will break in the weakest of storms. If you want to fix the world permanently, you cannot do so by simply removing all obstacles magically. When those obstacles return your world will be even less prepared than they were before.

Lastly you make the assumption that you are capable of understanding the whole world, the political and cultural climate of every country, well enough that you can stop or adequately manipulate all the “bad” people and make sure the good ones are protected. You are not omniscient. This is not possible. You are bound to kill innocents in an effort to complete this endeavor, and you are certainly never going to kill every psychopath or misguided individual who fully supports capitalism.

You are Kira because you are holding onto the belief that if you just murdered enough “bad” people, the world would suddenly become and stay a better place, when in reality it’s just temporarily suppression. Those who would worship you would worship you for your power and dominance not for any doctrine of community or empathy. Even Those who you tried to help may face the fear that they’ll do something “against the party” and you’ll end them for it.

But hey maybe it could work, maybe the world would become a temporarily better place with less pain and destruction, but Light could make the same argument.

You are still slaughtering others under the delusion that somehow it will fix everything, that you would play the part of god perfectly and bring to pass a new world.

To paraphrase L: “I can guess your motive and why you're doing this. But what you're doing is evil.”