Automatically running LLM-written code (where the LLM might be naively picking a malicious library to use, is poisoned by malicious context from the internet, or wrongly thinks it should reconfigure the host system it's executing code on) is an increasingly popular use-case where sandboxing is important.
That scenario is harder to distinguish from the adversarial case that public hosts like Cloudflare serve. I don't think it's unreasonable to say that a project like OpenWorkers can be useful without meeting the needs of that particular use-case.