Ah okay, then I don't really disagree with you. However I think it's the nature of medicine and research to want to look for a better test, not just because fewer and simpler tests make the diagnosis easier, but it can help provide understanding of the underlying biology of the disease. It's far more useful to have two test with a combined specificity of 90% than 5 different complicated ones that only take you to 50%. So I think it's not necessarily about searching for one test that is perfect, but perhaps fewer and simpler ones that would make it less complicated to diagnose.

I think there are many cases where doctors rely on multiple tests to help establish a diagnosis, if only for the sake of validating their suspicions. However those tests also tend to reflect the underlying biology of the disease, so getting other indicators alongside that is ensuring reliability and accuracy. But when we have a disease with poorly understood aetiology, using non-specific tests doesn't help with feeling confident about a diagnosis.

For instance non-specific markers of inflammation like CRP and ESR are commonly raised in rheumatic conditions like rheumatoid arthritis, and a positive result in a patient with clinical signs of active disease is encouraging when you also have a positive rheumatoid factor (70% sensitivity) and positive ACPA (95% specificity). But raised ESR and CRP with joint pain alone doesn't really help you since those can coexist with other joint-involving conditions. Similarly before we had ACPA, rheumatoid factor was one of the main tests relied on, despite the fact that it was positive in other conditions, but we had very good clinical criteria as well as imaging tools. ACPA has helped make RA diagnoses more accurate and a negative result suggests other arthritic conditions, and this is important especially for considering treatment.

So yeah, I mean if there is research to show good specificity with a bunch of tests then we don't necessarily need to find some holy grail marker, but finding better ones is always going to be beneficial for diagnostic and therapeutic reasons. At this stage getting any good test(s) will be helpful but that doesn't mean the road should stop there in terms of researching better options for testing.