How do you store data in a decentralised way without have many redundant copies? The decentralisation of Blockchain is from many machines maintaining their own copy of the entire history. The entire xo dept I herebtly stores more data. Your suggestion is to literally store more data, claiming it won't store more data only suggests you don't know how blockchain works.

And that's not even including any overhead of implementing a Blockchain in the first place. Or the fact you'll be storing data on literally every user even if they never interact with your instance, pr even if their instance is entirely blocked from yours. And there's no way around that, if you do manage to selectively store some subset of users then when you do need to include that data you're trusting the subset of maintainers who do have that user's data which, initially, is only the user's home instance so we're back to square one.