Let's say a billionaire offers a new car to each one in your neighborhood. However, it's like this. You will get a new $12,000 Nissan Versa, your neighbor will get a new $120,000 Mercedes. Would you accept that deal? That's how capitalism works, it makes life better for everyone, but not equally better.
That isn't a very ethical system though. Think about it, it's much worse than that. Our total world agricultural output is 2790 kilocalories per person (7 billion) for one day. This means that I can take my fair share of that output for one day, and use that food for the next 1000 days (roughly 3-4 years). Yet the World Bank claims capitalism is solving hunger and poverty, it's been heavily criticized for skewing results and only taking into account non-regional poverty. An ethical system wouldn't produce as efficiently as capitalism, but ensure that the wealth being accumulated is fairly distributed through society. This doesn't necessarily mean equally, but fairly.
A top-down system does exist, always, because in any case someone has to make the decisions at the top. I guess a different system could be created in the future, using artificial intelligence, but today there is no way that one person can have a personal interaction with thousands or millions of other people. You can interact with one person out of millions, like we are doing right now, but you aren't interacting with each one of those millions. In the end, one decision is made, and there will always be many out there who disagree with that decision. It's always a political process, one person has to convince the majority that this is the right decision.
There are multiple examples of systems that aren't necessarily top down. You're right in that the people should elect certain figures and departments to take care of essentials like water and defense, but these people obey the public, not the other way around. Good examples are Rojova, Catalonia, Paris Commune, and the EZLN.
The beautiful thing about Anthropology is that it makes many arguments that claim to know how human society works, wrong. To look more into a viable alternative for a bottom up system of democracy, look into Council Democracies.
https://www.opendemocracy.net/ourkingdom/ivo-mosley/council-democracy-reform-must-begin-with-local
While in today's representative system, one politician can represent 100,000 to 300 million people. This level of democracy can derive power from the bottom and represent 400 million to 10 trillion people. The system relies on community decisions being made that only affect the community and sending direct and immediately recallable representatives to a higher council that represents the larger areas and larger issues.