Having a different description meta tag for each page helps both users and Google, especially in searches where users may bring up multiple pages on your domain (for example, searches using the site: operator). If your site has thousands or even millions of pages, hand-crafting description meta tags probably isn't feasible. In this case, you could automatically generate description meta tags based on each page's content.
For traditional SEO, this has meant some loss of key real estate. For SERP results pages that once had 10 positions, it's not uncommon now to see seven organic search results below a Featured Snippet or Quick Answer box. Rather than relying on PageRank algorithm for a specific keyword, Google search queries rely increasingly on ML algorithms and the Google Knowledge Graph to trigger a Quick Answer or pull a description into a snippet atop the SERP.
For example, let's say the keyword difficulty of a particular term is in the 80s and 90s in the top five spots on a particular search results page. Then, in positions 6-9, the difficulty scores drop down into the 50s and 60s. Using that difficulty score, a business can begin targeting that range of spots and running competitive analysis on the pages to see who your website could knock out of their spot.

I think ranking in organic listings is a lot about trusted links making trusted pages rank, making trusted links making trusted pages rank ad nauseam for various keywords. Some pages can pass trust to another site; some pages cannot. Some links can. Some cannot. Some links are trusted enough to pass ranking signals to another page. Some are not. YOU NEED LINKS FROM TRUSTED PAGES IF YOU WANT TO RANK AND AVOID PENALTIES & FILTERS.

Thick & Unique Content – There is no magic number in terms of word count, and if you have a few pages of content on your site with a handful to a couple hundred words you won’t be falling out of Google’s good graces, but in general recent Panda updates in particular favor longer, unique content. If you have a large number (think thousands) of extremely short (50-200 words of content) pages or lots of duplicated content where nothing changes but the page’s title tag and say a line of text, that could get you in trouble. Look at the entirety of your site: are a large percentage of your pages thin, duplicated and low value? If so, try to identify a way to “thicken” those pages, or check your analytics to see how much traffic they’re getting, and simply exclude them (using a noindex meta tag) from search results to keep from having it appear to Google that you’re trying to flood their index with lots of low value pages in an attempt to have them rank.
However, that’s totally impractical for established sites with hundreds of pages, so you’ll need a tool to do it for you. For example, with SEMRush, you can type your domain into the search box, wait for the report to run, and see the top organic keywords you are ranking for. Or, use their keyword position tracking tool to track the exact keywords you’re trying to rank for.