There are well-defined interfaces for specific sub-classes of telemetry data. Prometheus provides a set of interfaces for metrics which are pretty battle-tested by now. There are similar interfaces for logs and traces, authored by various different parties, and with various different capabilities, trade-offs, etc.

There is no one true interface! The interface is a function of the sub-class of telemetry data it serves, the specific properties of the service(s) it supports, the teams it's used by, the organization that maintains it, etc. etc.

OTel tries to assert a general-purpose interface. But this is exactly the issue with the project. That interface doesn't exist.

OTEL is a set of interfaces, so I’m not sure your last point applies. I do agree that battle tested things like Prometheus work great, but why not have a set of standardized interfaces? There is clearly a cost to having them; for some projects this may be too much. For the projects I’ve used it in it let me spin up all the traces and telemetry without thinking hard.