> Sure, of course you would make practical decisions about what kinds of tests to administer, and not proactively administer the tests that have significant negative side effects.

The harm is from investigating the screening test result and not the test itself.

> If it became a common thing for cancers to be detected, but the detection could reliably say “this is likely low impact, we should just keep an eye on it but not treat it”, this would be a lot less scary

This is already the case for some like prostate cancer and certain lymphomas.

> Cancer diagnoses are partly so scary right now because we’re often mostly catching cancers that have progressed and are causing symptoms

The most aggressive cancers are also the least likely ones to be diagnosed by screening due to growth rates, screening intervals and diagnostic test limitations.