The technical bar is low by design. Most sites clear it without trying. The problem is that when a site fails it, the failure is usually invisible from the browser, the page looks fine to you and is unreachable to Google.
Googlebot must be able to fetch the page
Blocking happens in more places than people expect: a robots.txt rule inherited from a staging environment, an IP or user-agent firewall rule, a bot-protection service, a country redirect, or a consent wall that returns nothing until a cookie is set.
The page must return HTTP 200
A page that returns 404, 410, 500 or 503 will not be indexed. Watch for soft 404s, a page that says “not found” in the text but returns 200. Google detects these and treats them as errors, which is usually not what the site owner intended.
The content must be indexable
The page has to produce HTML that Google can read after rendering. Pages that render entirely client-side can work, but only if the JavaScript executes successfully within Google rendering budget and does not depend on user interaction.
Alien Road recommends: test with the live URL, not a local copy. Use the URL Inspection tool in Search Console and read the rendered HTML, not the source. We have repeatedly found sites where the source contains the content and the rendered output does not, because a script failed on a resource that was itself blocked in robots.txt.