At the risk of hijacking the comments, I've been trying to use OTel recently to debug performance of a complex webpage with lots of async sibling spans, and finding it very very difficult to identify the critical path / bottlenecks.

There's no causal relationships between sibling spans. I think in theory "span links" solves this, but afaict this is not a widely used feature in SDKs are UI viewers.

(I wrote about this here https://github.com/open-telemetry/opentelemetry-specificatio...)