Google de-indexed 1.7k pages on my WP site, trying to figure out why [duplicate]

I created a site in WordPress with a mass page plugin called Mpgwp.com which dynamically creates pages with a spintax doc and spreadsheet. It’s an affiliate site going after local keywords. The pages are duplicates structuarally, but all the content is spun from a spintax doc, so the actual content is not the same across each page. Google initially indexed them and I was getting traffic, and then steadily started de-indexing them. I’m assuming Google just doesn’t like the pages, altho they are actually content-wise better than most of the other spun pages in the SERPs for these pages (many other sites taking the same strategy). The pages work fine and the plugin dev. is stumped and suggested I come here to ask. There are no manual actions or other penalties. Either goog hates the content and thinks it’s spammy, or there’s something tecnically wrong here.

He mentioned that the "disallow" in my robots.txt might be causing it? robots.txt

This is the message in my search console: "Crawled – currently not indexed: The page was crawled by Google, but not indexed. It may or may not be indexed in the future; no need to resubmit this URL for crawling." search console message

This is an exmaple of one of the pages: https://trailersconnect.com/construction-trailer-rental-in-madison-ca/

Does anyone have any ideas what I’m doing wrong?