Well maybe I'm wrong but I don't see how PoW is not centralised so you have to explain me instead of saying "it's not true".

No one is solo mining. Everyone is on pools. People tend to chose the biggest pool.

There is a high competition for specialised hardware. When Bitcoin started, everyone could mine it on CPU, then GPU, then FPGA and now only an elite can afford the $10K ASIC. The production of the hardware is highly centralised and the people that have access to it are decreasing everyday.