PoW, (D)Pos, and Ethereum's faulty consensus design... none of it is decentralized.
Depends what you understand by "decentralization" and how much of it you "need" to make your platform work. You need enough to make it trustless and extremely expensive to attack. Both POW and POS are oligopolies, aka several people / groups will end up controlling most of the wealth, because they invest most early, wether they buy it or mine it. If you build a system that aims to become money like bitcoin, it will become oligopoly because that is how the world works. That doesn't necessarely make it centralised. Bitcoin's mining became centralised in China because of the asics. Ethereum's mining is not centralised because you can even mine in EU with expensive electricity, for example, and still be profitable.
So, ethereum and other gpu based mining blockchains are decentralised enough. More than enough.
However, if you want close to perfect decentralization then you need to build a specific use case project, maybe a social website / blog like steemit but without an economic system turned into a piramid scheme.
You should stop seeing things in black and white. You can't possibly expect for bitcoin to have 16mil users with 1 bitcoin each, or 1 asic each and a full node to be perfectly decentralised. That's not how the world works. However bitcoin and other asic pow blockchains are a bit too centralised because of that, asics. Luckily ethereum doesn't support asics and the mining is not centralised ( unless you consider pools, but they're made of thousands of small miners ).
