You've raised some common and valid criticisms of how ADHD is diagnosed.
1. On standardized scales being "meaningless": The term "standardized" here doesn't just mean a consistent set of questions. It means the scoring is normed against a large, representative population. So when a parent says their child "often" loses things, the scale helps a clinician determine if that "often" is statistically significant compared to other children of the same age and gender. It's a tool to quantify subjective reports. You're right that any set of symptoms can be standardized, but these scales are specifically designed to measure the frequency and severity of behaviors outlined in the DSM/ICD criteria. They aren't a standalone test, but one data point in a larger clinical picture. Most psychiatric conditions rely on this kind of structured self-reporting. The people working in this field work very hard to apply statistics properly when designing and running these tests; it's so far from random it's not even funny.
2. On CPTs: I agree that a CPT is an artificial lab scenario. That's a well-known limitation called a lack of "ecological validity." No one claims it perfectly replicates real-world focus. Consensus statements are clear that CPTs are insufficient for diagnosis on their own. Their value isn't in definitively saying "you have ADHD," but in providing an objective measure of things like attention lapses and impulse control that can supplement the subjective reports. If someone's self-report suggests severe inattention but they score perfectly on a CPT, that's a data point a clinician needs to investigate further. It can help in the process of differential diagnosis. The studies you linked highlight its limitations, which is consistent with the consensus view that it's a supplementary, not a primary, tool.
3. On multi-informant reports: You say these are "as subjective as you can get," which is true, they are subjective. The entire point is to gather subjective reports from multiple contexts to see if a pattern emerges. A core criterion for ADHD is that the symptoms cause impairment in two or more settings (e.g., home and school/work). If a child is only described as hyperactive and inattentive in a boring classroom but is a focused and motivated musician at home, a good clinician would question an ADHD diagnosis and look for other factors. The goal is to see if the problem is with the person's underlying regulation skills across environments, not just their "fit" in a single, artificial system.
4. On the DSM and clinical interviews: The word "often" is intentionally not given a hard number because it's relative to a person's developmental stage. "Often" losing homework is different for a 7-year-old than for a 30-year-old. This is where clinical judgment, guided by the DSM criteria, comes in. As for the symptom overlap, you're describing a feature of many polythetic diagnostic systems, not a flaw unique to ADHD. It recognizes that the disorder can manifest differently in different people. The clinician's job isn't just to count symptoms, but to assess the entire pattern, determine the level of impairment, and critically, rule out other potential causes for those symptoms (anxiety, depression, trauma, etc.). The diagnosis is a synthesis of all this information. Again, standardized test scoring DOES have the effect of giving a "definition" to the term "Often", because when thousands of forms are filled in, individuals' different definitions of the term converge in a statistically significant way onto a concept that is meaningfully comparative.
5. Finally, your historical point is interesting. Descriptions of ADHD-like symptoms date back centuries, long before the DSM. Sir Alexander Crichton wrote about "the incapacity of attending" in 1798. The diagnosis wasn't just invented out of thin air in the 20th century. It's a modern label for a pattern of behavior that has been observed for a very long time. The research and technology we have today are being used to better understand its neurobiological underpinnings, not to retroactively justify a "socially agreed upon disorder".
I'm really curious what the next century of study will do to illuminate this condition. I suspect we will have significantly greater understanding of the role of genetics and perhaps, one day, a blood test will diagnose ADHD.