data manipulation is virtually impossible.Check out blockchains like Holochain and Sia Coin.In any circumstance of failure of the blockchain,each block has complete copies so that no data gets lost.This file decay you speak of can be combated via better hardware developed in the future & competence

If I want data integrity I can simply calculate a HMAC, I don’t need an entire blockchain network for it. The problem is also not just integrity, but availability. Your “solution” is based on having multiple distributed copies .. why do we need blockchain for that?