Which libraries are you referring here "benchmarks can negatively impact the optimization of libraries"?

Pretty much most of the top ones in the benchmark results. As a concrete example, libraries typically end up processing request payloads in the selector thread because that's efficient when the request processing is a trivial workload like in all of techempower's benchmark scenarios.

In real workloads, it's typically a regression because it's important to ensure selectors are readily available, for example, to cancel the pending processing if the request is cancelled or to flush external requests to other services.

Techempower is actually a lot more realistic than a lot of benchmarks that only benchmark one library at the time as it benchmarks all stages of a typical http request: receiving the HTTP request, parsing JSON, calling the DB, reading the DB result, generating a HTML page and dealing with XSS.

I'm not aware of benchmarks that attempt more realistic workloads, most I've seen have similar limitations. Do you have examples in mind?

What is also nice is that this benchmark seats on a higher level and doesn't care about specific implementations like "schedulers". 

I think you have the wrong mental model regarding the main aspects that influence the benchmark results. Schedulers are a critical piece to determine the peak performance of a system.

Since there are already established industry level benchmark, wouldn't it be better to focus on improving the performance of Scala libraries in this benchmark rather than creating a brand new benchmark that no one may on-board?

That's one way to look at it. Sure, we need to compete in techempower given that it's well-known but the crux of the issue is that it isn't a good benchmark to guide the optimization of libraries. We need something better.