History of the Error
Starting from 8.0 any creation must explicitly be invoked by a router. The shard will stop the write operation and throw cannotImplicitlyCreateCollection exception, which will cause the router to retry by running first (explicitly) a creation and after the same write that triggered the creation again.

The issue

In case of concurrent operations, the router can exhaust the attempts and show the error to the user. This can be a problematic because the error can be very confusing for the user. The exception means the shard is not authorized to create the collection implicitly. From a user perspective (which talks to a router) the implicit creation is allowed.

Goal

The goal of the ticket is to assess weather the error should be masked and presented to the user in another form.