What we see in practice with all extant implementations of blockchains is increasing centralisation. Because computing hashes is the sort of computation whose efficiency per watt greatly increases with more and more specialised hardware. Thus the Bitcoin situation, where the promise of everyone being able to mine a few coins has become a small number of Chinese mining pools; altcoins do no better.
Most altcoins are Proof of Stake, where mining via computing hashes doesn't take place. "Blockchains" isn't limited to Proof of Work, you can even get non-PoS/PoW blockchains such as Hyperledger.