This wealth concentration in cryptocurrencies is a direct result of their front loaded emission. Half of all Bitcoin was emitted in its first 4 years; about 70% of current Dogecoin was emitted in its first year; 70% of current Ethereum was emitted in its first block.
Reducing wealth concentration (to be closer to the one in fiat) requires a more even coin distribution, such as a purely linear emission of 1 per second forever.