[ch2026]

Because nobody uses mongo for the reasons you listed. They use redis, dynamo, scylla or any number of enriched KV stores.

Mongo has spent its entire existence pretending to be a SQL database by poorly reinventing everything you get for free in postgres or mysql or cockroach.

[yearolinuxdsktp]

False. Mongo never pretended to be a SQL database. But some dimwits insisted on using it for transactions, for whatever reason, and so it got transactional support, way later in life, and in non-sharded clusters in the initial release. People that know what they are doing have been using MongoDB for reliable horizontally-scalable document storage basically since 3.4. With proper complex indexing.

Scylla! Yes, it will store and fetch your simple data very quickly with very good operational characteristics. Not so good for complex querying and indexing.