My barely literate 75 year old grandma could watch soaps with Romanian subtitles in the evening :-))
It's just a matter of practice. And of watching on a big screen, I'd say.
I agree neither dubs nor subtitles are 100% faithful to the original. By necessity, they cannot be. There's no such thing as a perfect translation even with books, but with TV/cinema you also have to keep the pace, which makes things doubly difficult.
Even then, just hearing the original language, even if you don't understand the words, conveys essential emotion. I like to hear the original voice actors, which are essential for the cartoon/anime (even more with live action movies, of course).
That said, subtitles can be very distracting. You end up focusing on the word and missing things in the scene/shot as well as the background.
Also the subtitles are not always faithful to the dialog. A good example of this is watching One Piece in English w/ Subs on Netflix. The spoken dialog will be one thing, the written will be another. I have some Japanese knowledge and can tell you that the subs(and the dubs) definitely do not reflect the feeling in some scenes.