I am writing articles for metanet.id. My first article: …

bitcoin nodes are capable of pruning “provably unspendable” UTXOs for efficiency, which include OP_RETURN data

immutability is not availability

so you cannot delete or alter data, but it can become unavailable -- potentially permanently unavailable

I agree nodes can prune and not all nodes will store the whole history. I assume some will and people will pay for access just like they currently pay for access to internet. Some might pay for 100% access, others for last 30 years, others for 7 etc.

Also with miner-id implemented, you could pay a miner to store an specific op_return for a certain guaranteed period, legally required for the specific data, like a minimum of 7, 30, or 100 years etc