Even just the data for a free tier, and even if just saved for one single day, will be too much for any individual to be stored.

For paid tiers it can work, but those relays must then be run hyper professionally, constantly adding more storage, guaranteeing zero downtime and zero loss of data. Only very few relays will have the expertise to pull this off - and that means, a handful of relays will store everything, and those relays can be censored by the state.