There have been plenty of cloud services that have shut down and taken their data offline. And plenty of current ones deleted data after users have gone inactive. Or require constant payments to keep accounts active. Cloud, as it exits now, is not the answer to the archival question.
They take your data down pretty quick when you die and stop paying for it. And as much as we all want to think AWS and GCP and Azure are sticking around forever there’s no reason at this time to believe they will be around in 100+ years.