--> I deal with this problem by running both NoScript and uBlock Origin. If some site (typically a news site) tries to run scripts from 15 sources (literally!) and I don't want to figure out which two or three really need to be whitelisted, I'll temporarily disable NoScript and let uBlock Origin knock out the dozen that are just trackers and crap.
That's what I like about Opera/ScriptSafe. Once you figure out which sites to blacklist (either specific pages or the whole domain), you never have to deal with them again.
It's a pain at first, deciding what to let through and what to block. Unless I am certain, I will just block the specific page I believe to be a problem. If more pages show up under the same domain that I want blacklisted, I'll block the whole domain. Pretty much the same process for me in whitelisting pages and/or domains.
I am willing to live with the sterile look and feel of Opera, but learning they were sold to a Chinese company last year is concerning.
The actual whitelist (or blacklist) can be the current page's domain, i.e. www.youtube.com or its entire domain, meaning all subdomains are also whitelisted. The same scheme is applied for blacklisting domains.
NoScript is "mostly" a whitelist-based blocker and, by default, blocks all active content from everywhere. NoScript also allows a form of blacklisting that sounds the same as what you are talking about. NoScript calls it marking them explicitly as "untrusted." There is no operational difference between NoScript blocking a site because you have marked it untrusted vs. blocking it because it has not been whitelisted. However, when you pop up the list of stuff that NoScript is blocking on some page, it leaves out the stuff that you have already marked as untrusted. As you say, you never have to deal with them again. (If you need to see the untrusted stuff on some page, you can click on the "Untrusted" submenu on the popup listing of what it is blocking.)
Is ScriptSafe strictly an Opera goodie, or is it something I can experiment with in the browsers I am considering (Pale Moon, Waterfox, Chrome)?