What percentage of your site is saved in Google index?

In the past years, I've been noticing Google's declining ability to save multiple website contents into its index. Yes, it does craws the website, and most of the links, but actual amount of pages in Google has been declining in all websites that we know of.

While Microsoft is indexing and saving at a 5-10X rate more than Google.

What was your experience with Google Index?

How to check: 1. Open Search Console 2. Go to Experience > HTTPS section. Is the number of pages in the HTTPS report relative to your website's real pages?

Google lacks the resources to index the whole web now and is now behind its competitors like Microsoft?