Generally, Google has said that when pages are not indexed and there are no technical issues, the reason it might not be indexed is that the page does not meet the quality marks to be included in the Google Search index. But John Mueller of Google said even high-quality pages aren't guaranteed indexing.
John said on X, "A page can be of high quality and still not be indexed - it's not guaranteed." "Pushing it through these tools doesn't guarantee that they'll stay (or even become) indexed. There's just a lot of good (& also questionable) stuff on the web, shrug," he added.
Here are those tweets:
A page can be of high quality and still not be indexed - it's not guaranteed. Pushing it through these tools doesn't guarantee that they'll stay (or even become) indexed. There's just a lot of good (& also questionable) stuff on the web, shrug :)
— John, aka "a total bell cheese" (@JohnMu) September 28, 2023
Google has said that if you need to submit your pages to Google, you may have some quality issues with your site.
Generally, Google wants to crawl, index and rank high-quality pages. But it is not guaranteed that Google will index everything, all the time, even if it is high-quality. It would likely be a miss if Google did not but Google is not perfect.
Forum discussion at X.
