Yet there is no evidence that they have done so. There is no objective way of testing whether language learning has improved. But so-called objective tests cannot be used for that purpose either. They have not been used consistently in the same 'concentration' over the period they have been in use. Moreover, people can be trained in the techniques of multiple choice and other 'objective' tests, so they are not really objective at all.
Impressions are still the only thing one can go on.
As far as English as a foreign language is concerned, my personal impression is that standards have declined somewhat. Most people would surely agree that good professional cooks, carpenters, surgeons or violinists are people who cook, do carpentry, carry out operations or play the violin expertly. In the same way, professional linguists, genuine ones, are experts at learning languages. It is surely also reasonable to think that the task of those who teach would-be cooks, carpenters, surgeons or violinists is to show their apprentices and students how to cook, do carpentry, carry out operations or play the violin. We find pedagogy, methodology and linguistics.