cheaply dropping log msgs you cannot handle is absolutely essential for an observability system - otherwise excess load can take down the logging infra which can (if msgs aren't dropped) take down the prod network/app trying to send reliable log msgs.
Audit logs are a distinct feature.
That's fine if you plan for it and can clearly delineate which logs can be dropped and which can't. The challenge is that most applications log to a single stream that consists of both high and low-priority logs muxed together and is sent to a single destination, making it impossible to distinguish the two, and there's only one receive buffer.
Excess load can't take down a well-engineered log collection infrastructure. There can be overload, but the backpressure should propagate downstream and senders and intermediaries should buffer locally if needed. Once the collectors are able to catch up again, the spooled messages will be dispatched, and the backlog should recover.
A well-engineered logging system for sites that care about integrity and durability should look a lot like a distributed message queue.
> Audit logs are a distinct feature.
In my experience, this is not always as distinct as one might hope. On multiple occasions in my career, a customer demanded we perform research using our logs to answer, and the information they sought were not in the class of logs that were considered "audit logs" in advance. Everyone chooses differently what qualifies as "audit logs"; it doesn't have an objective definition.
If you are doing massive log streams with mixed priority/durability, use named queues if you have different priority and retry and durability needs. You keep bringing up edge cases, but they've already been considered and solutions already engineered and available in every major syslog implementation.
I didn't say they those choices aren't viable; I'm strictly talking about architectural decisions. You can solve the problem with different solutions, be they rsyslog or otherwise. That said, I probably wouldn't go with rsyslog as my default choice anymore since the world is moving on to OpenTelemetry.