Our site has exactly the same ‘problem’ as Mishwarek states and I’m also looking for a solution that doesn’t block Google’s bots from accessing the content (e.g. robots.txt) as this causes other real problems.
I see a lot of these “problems” on some of my websites in Google Search Console. These include secure login pages, restricted pages (requiring login to access), and completely private sections of my sites (in which I’ve decidedly blocked Google).
There are a lot of things Google’s software will find and complain about… that you should either ignore (because there’s nothing user-facing on those URLs, you’re not trying to rank them, and the work to provide a “fix” is non-trivial) or you should decidedly block Google from accessing (for security and privacy reasons).
That’s why Google gives you a tool in search console to tell them to IGNORE such URLs.
Do you really want people to be snooping on your website and seeing all your installed plugins like this?

It’s this same directory indexing that I’m talking about that creates a page listing all your images, that’s also created the above page listing this website’s plugins (and the content of any other folder).
If the web server is properly configured with Directory Indexing turned OFF, the above shouldn’t be happening (and your images shouldn’t be listed either).
(Note that if you open /wp-content/plugins/ on your domain and only see a blank screen instead of a listing of your plugins, it’s because the WordPress developers realized many people have improperly configured webservers, so to avoid strangers browsing your website’s folders and seeing all your installed plugins (among others), they now place a blank HTML file in most of the folders that ship with WordPress. But, of course, any new folders you create… including the monthly “uploads” folders, will not automatically have this “protection”.)
I would like some guidance if possible on how to apply some basic CSS (sizing/viewport setting) to ‘false’ pages with a link structure …/wp-content/uploads/*
Now, if you REALLY want to keep directory listing enabled… note that those index pages are NOT generated by WordPress, but by the web server itself. So you can’t simply apply CSS in WordPress to control that display.
CSS-Tricks has a tutorial to style directory listing pages:
https://css-tricks.com/snippets/php/display-styled-directory-contents/
Note that 1) You don’t apply the code in WordPress, as WordPress has nothing to do with it… 2) Even with sample code, it’s not trivial to get working… 3) The code in the downloadable files does not have sub-directory support, so you’ll need to adapt it somehow so your subdirectories will inherit the style (see the comments section for sample code).
Again, the real solution to this is to disable index listing in your webserver, ignore the Google warning, or ask Google to ignore those URLs.
If you decide to disable directory indexing, your best bet is to contact your host. If they won’t help, here are some DIY resources:
WordPress Plugin: https://www.ads-software.com/plugins/prevent-direct-access/
Good luck, and stay blessed!