guys - to be on the safe side, go to your google webmaster tools / sitemap / on the right side, you will see 3 sections: all content type, web pages, images.
click on web pages and you will see the trend line for both submitted and indexed. this is a 30 day view. here is what I did:
may 17th: yoast / media section / made "Show Media in search results?" NO
Redirect attachment URLs to the attachment itself? was set to NO as well.
Had google fetch my website again
May 21st: number of indexed pages went from 325 to 174 and images went from 282 to 132
May 22nd: ranking for few keywords increased
so what I am trying to say is this: do not just rely on making some modifications in yoast, make sure you see the result in google sitemap section. also, having google fetch your side would not hurt after your modifications
p.s. now, I have "Redirect attachment URLs to the attachment itself?" as yes, which hides the option for ""Show Media in search results?". also, I have installed
https://wordpress.org/plugins/attachment-pages-redirect/ (source:
https://www.seoblog.com/2018/04/wordpress-attachment-hurt-seo/)
will let you kow what changes I notice