Target Language L2 in classrooms - TO BE CONSIDERED!!!

Many are the ideas around this topic, but there is only one reality under my humble opinion, the more we hit L2 in our lectures, the more our students will acquire the target language. Yes, sometime is "impossible" to achieve this since there are concepts complex to explain and things that for its importance must be considered to be developed in L1 (mother tongue),

I repeat, its only an option, if we use L2, easy grammar, slowly, there is not need to use L1, it sounds like impossible to do because at least here at my country, nobody does it, and it seems to be totally a new generation of language education, but it is proved to be the ultimate best way of teaching this.

Ok here is an easy example, math class, is there any teacher around the world that does not use the blackboard and formulas and numbers? is there any science and nature teacher that does not use the environment as the learning mirror...same are languages, teachers have to present what is to be achieved...other than this are bad teachers that dont give a peanut for their students, all they want is money in their accounts by end of the month... and we are already in XXI century.