While it is possible to use ES as your primary store, doesn’t mean it is a great use-case. Pushing ES to durability takes resources (people, time, compute) and rigor.
For a blog site this feels like overkill. Your priorities are durable low-freq writes, and more freq-reads. Hands-free day-to-day maintenance, and simple recovery mode such as restore. Caching (and optionally queuing) can absolve sins of many topologies to fulfill these requirements.
ES brings a much larger surface area than just store blobs and metadata. Big tax to gain free-text search - which while interesting most users will almost certainly never use (thank Google for that)
Focus on a cheaper, lighter, database engine that is durable, checkpoints regularly, and has simple, testable backup/restore processes. Ship the backups somewhere e.g. S3