I understand what it does, I just don't understand how to use it effectively. Like I just tried it: I enabled uMatrix and went on the website of the NY Times. I end up with a rather large matrix with a bunch of domains like "a.nytimes.com", "api.nytimes.com", "samizdat-graphql.nytimes.com", "optimizely.com", "js-sec.indexwww.com" and many others, includind a bunch of google and amazon domains.
How am I supposed to figure out what I should whitelist in there? Trial and error?
There are a few obvious candidates for blacklisting (amazon-adsystem.com for instance) but I'm sure that those would already be blocked by my uBlock filters. Actually so far uBlock with a few ad + privacy enhancing filters seem to do a decent job which makes uMatrix even more frustrating because I feel like I'm doing something by hand that uBlock does just fine automatically.
But at the same time I often see people praise uMatrix here on HN and that makes me feel inadequate and noobish so I really want to understand what I'm not understanding.