The mining power is inaccurate way of showing decentralization of bitcoin.
First of all mining pool does not equal miners. I have a miner pointed at slush pool does that mean the mining pool is me? The mining pool is like steem delegation. The miner can withdraw support from a pool. This is happening to Antpool and btc.com
Also with the introduction of new mining companies the distribution of hashpower is weakening bitmain hold.
This is the current one:

Source: https://blockchain.info/pools
And also The miner are not the dencentrzled part. It the nodes-remember UASF? Nodes are what matter in bitcoin and fake nodes are very easily seen. Also since bitcoin has no lead dev the development of bitcoin is the most decentralized.
And for the miner part with the introduction of halong mining Bitmain dominance in bitcoin mining has dropped. A much need computer has arrive to asic and samsung is helping halong mining in the quest for an alt mining company. With the bad press Bitmain has-less people buy for them.
To counter Asic negativity
In theory, Asics are better than Gpu and maybe more decentralized. Asic= consistent hashrate and loyalty to the chain. Asic mean that you are not into only for the money but to help the chain since you can only use the asic for that. In gpu you can switch any time to other gpu coins. Many gpu miners are into only for the money by using nicehash and auto switch pools. Asic are supposed to decentralized by the the fact more than one company are making them.
Right now the problem with Asic is that one company makes them-Bitmain. If Halong mining is one of the few key reason why bitcoin was against changing the algorithm. It might be one of the last test to show if Asic can truly be decentralized in theory.
I kinda like POS(crying out load bitcoin is going to use POS in its sidechain tech . )
But current POS has a flaw who know it could be made better. People are researching them. DPOS does look like one of the best types of POS
Currently POW is better in my opinion.
While yes POW does seems like an energy waste it not. This work is necessary to make the chain secure. In POS, the stakers who owns 10% of the supply will mint 10% of the supply, and won't cost them anything much.
In, POW you have to battle against everything. You have to buy new miners to keep up, pay electricity, cool the machines, buy new ones.

Pos makes it so that 51 attacks are harder bc they are little their investments on the line. Pow is somewhat even harsher. Not only will their rewards lower if 51% attack done, the coin down=machines useless. This is amplified by asic machines which effectively locks the minier rig to mine only that coin.
Pow can be improved even more by making useful mining aka finding primenumbers. This is being researched in bitcoin.
Also POW in theory should encourage miner to look for greener energy and maybe already doing it.
https://steemit.com/mining/@sames/bitcoin-mining-pow-the-truth
And your first point-Nakamoto most likely will never tough his coins. But after 100 years the first problem will slowly be loved his most likely could of died. And no one really know how much he owns it just that much of the original mining coin have not been moved which could mean that it Nakamoto.
Bitcoin is the great experiment and the most decentralized of all coins.
A blockchain can not work without a bitcoin like coin. Otherwise it is just a fancier database.