ha i've felt the same way! it seems like none of their examples are the straightforward, common use of a thing and they like to pick the most obscure use-cases to highlight!
i really didn't want to admit to this, so rather than give in to my initial frustration, i decided that MDN is what i aspire to understand and as a beginner i'm ok with using the pariah W3Schools ... as long as i go back to MDN for all the "note" sections where they really explain the "yeah you could do it this way, but it's a bad idea because blah blah blah" cases. those are often completely missing from W3Schools.
it's worked so far, i've gotten better and better at understanding MDN descriptions and examples.