Curious what you mean about the design of OpenTelemetry precluding efficient implementation?
Its important to know what audience you're building for. I believe the audience for otel consists largely of companies that don't look anything like Google. So its fine to sacrifice that last bit of perf gain if it means the code is easier to use and maintain.
FWIW, it also appears that companies like Google would fork or reimplement such systems anyway.
Looks like Opentelemetry (at least its precedessor, OpenCensus) is originated from Google. From OpenCensus website (https://opencensus.io/):
> OpenCensus and OpenTracing have merged to form OpenTelemetry
> OpenCensus originates from Google, where a set of libraries called Census are used to automatically capture traces and metrics from services.
Original internal Google tracing system was probably designed for scale. And opentelemetry's design is probably based on that internal system.
So, maybe poor performance is just an implementations issue.