My experience is pretty much the opposite.

I've learnt Spanish during the last 3 years pretty much only by listening and watching TV (mostly listening to podcasts). I haven't really tried to memorize anything, and have above all tried to avoid being bored.

I also avoided reading and writing for quite a long time, trying to focus on spoken language.

I wouldn't say that I "master" Spanish yet, but by now I can enjoy all sorts of films, TV, radio and discussions in Spanish. I still miss the occasional idiom (especially the kind of slang that teenagers use), though, but it seldom bothers me.

Also it turned out that learning to read when you already know how to speak (and can read other languages, I suppose) is actually quite easy. By now I can read novels etc. in Spanish without too much effort.

Maybe I would have been able to learn Spanish even faster by using a more boring method. But then the cost would have been much, much higher for me - being bored for endless hours on end is a very high price to pay.

And I'm pretty sure that I would have given Spanish up a long time ago if I had followed that route.