I think the key is to allow the learner to develop an innate understanding of the grammar trough natural usage, instead of memorizing a list of formal grammar rules to apply. That would mean learning a second language like we learn our first. Every child has a very good innate understanding of the grammar of their mother tongue long before they are introduced to concepts of formal grammar, E.G. a 6yo can use verbs without knowing they are called "verbs", and can assign the proper tense long before they are introduced to the formal rules of conjugation. So, as a child learning a mother tongue, the study of formal grammar rules should be introduced eventually to a 2nd language learner, but not before the person has an innate basic understanding of the language.
The idea that adults should learn a second language as if they were toddlers has no merit whatsoever.
For one thing, you don't want to spend three years babbling; you are not small and cute.
Grammar rules don't have to be "formal" (and, anyway, real grammar defies formalization). They are just sentence patterns, with examples.
If you try reading material without front-loading on a working knowledge of, say, the most common 100-200 sentence patterns, you're not working as efficiently as you could be.
The sentence patterns in a grammar dictionary don't give you the grammar, only a way to navigate in the language so you can get the real grammar faster, with less time-wasting guesswork.
