How to know when you can and can't monetize televised content?

Hey, so, a question arose in my head from the gentleman who posted about getting millions of views and having 100k subs with Netflix series clips, but he can't monetize it (because it's clips from shows).

So, my question was: if you're pulling clips from the series on TV you obviously can't monetize, BUT if you're showing short clips and talking over them or just showing stills and talking over them it can be monetized? Where is the line in the sand drawn? I've always wondered this with the sports compilations, as well.

the line is very blur, it said if you modify the content and change the conent meaning, ea use as compilation, news report, review. it should be fine. but it is gray area withou spesific point.