I work on LLM benchmarks and human evals for a living in a research lab (as opposed to product). I can say: it’s pretty much the Wild West and a total disaster. No one really has a good solution, and researchers are also in a huge rush and don’t want to end up making their whole job benchmarking. Even if you could, and even if you have the right background you can do benchmarks full time and they still would be a mes…
The big problem is that tech companies and journalist aren't transparent about this. They tout benchmark numbers constantly, like they're an object measure of capabilities.
The general populace doesn't care to question how benchmarks are formulated and what their known (and unknown) limitations are.
That being said, they are likely decent proxies. For example, I think the average user isn't going to observe a noticeable difference between Claude Sonnet and OpenAI Codex.