There are so many words to learn!
I often see people working their way through newspaper articles and writing long lists of words into an exercise book. It is painstaking and time consuming. Usually the learner does not choose the article for study. The teacher chooses it. The words are written down but they do not enter our usable vocabulary until we have encountered them many times in different contexts.
There is nothing wrong with this approach, which is perhaps the most common way in which intermediate students of English study. However, it is just not going to enable the learner to cover the vast amount of material necessary to become really fluent and literate in English.
There are so many words to learn. One has to meet these words in so many different contexts. The method of study has to be more efficient. Efficiency is achieved when the learner can choose content of interest and at an appropriate level of difficulty. The learning of words and phrases is made much more efficient when we take advantage of the wonders of electronic text to link new words and phrases to the contexts where they occur.
The key reason why The Linguist system works for so many intermediate learners is the enjoyment afforded by being able to chose content and the efficiency of saving new words and phrases to a database for systematic review. This is all combined with repetitive listening and reading, writing and speaking.
There is just so much to learn, that efficiency becomes a key factor determining success or failure.