Googlers are often being asked about why content on specific websites do not rank or are not indexed. In this last case, John Mueller of Google responded to one request saying "We just don't index all content - complaining about it on Twitter won't change that."
Google has been saying they do not index everything for years, Google simply won't index all your pages and it is impossible for Google to index everything, Google said.
John added that complaining loudly on Twitter won't help.
He kind of went off a bit on it:
You're not new to this - you've probably worked on complex systems too. I don't quite know what to make of your loud tweets trying to solve this, but I get that it can be annoying when you have high expectations and an algorithm doesn't fulfill them.
— 🍌 John 🍌 (@JohnMu) May 20, 2021
Keep in mind, a month ago, Google came out with a form to report indexing issues. So you can use that form if you want and not complain on Twitter.
Forum discussion at Twitter.