Too Long; Didn't Read
There are multiple reasons to believe that calling Ethereum decentralized waters down the definition of decentralization. Many people remember when the game CryptoKitties clogged their network in the past, and during that time period transaction processing times were dramatically slow. Another problem that you have is that the development team hasn't set a max supply and it is more prune to hyperinfalation. This gives Vitalik more control than other cryptos give to development teams that have a set max supply. This means the big corporations that people are trying to shift towards decentralization actually have a large amount of control on these forms of alternative tech.