Google’s John Mueller said on Twitter just because your Google cache link is not showing up in the search results, it does not mean your pages are deemed low quality in Google’s eyes. It just means Google has yet to cache the page or something it technically stopping Google from caching the page.
Here are the tweets:

no
— John ☆.o(≧▽≦)o.☆ (@JohnMu) September 7, 2017
Just to remind you some other cache tips… The cache date is not the last crawl date, Google doesn’t show a new cache page for each crawl.
So I don’t think Google’s cache information has any indication of page quality in Google’s mind.
Also, here are more cache tips around this from John Mueller in the video hangout from just a couple days ago:

Via @johnmu: The cached page is the raw html of a page, not rendered version. Rendered version is used for rankings: https://t.co/7zoSQ7d1ZO pic.twitter.com/uhnlVDmKjR
— Glenn Gabe (@glenngabe) September 7, 2017

Via @johnmu contd: The cached page should *not* be used for diagnosing technical issues. Could also show a 404… https://t.co/7zoSQ7d1ZO pic.twitter.com/aGHckrpqd4
— Glenn Gabe (@glenngabe) September 7, 2017
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Forum discussion at Twitter.

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