At this point in history, the knowledge is there and again may be had by any sincere man or women. To be fair, many Tantric texts were written rather allegorically or with symbolic language, Twilight Talk, so that the inner meanings behind the literal meanings were unable to be grasped by the ignorant. Or words to the effect. I believe their intent was simply to separate the sincere from the curious. Proper attitude, or Will, can transform the mundane to the highly spiritual.
External worship leads to internal worship.
Internal worship purifies the mind. Purity of mind intensifies concentration and meditation. The potential for growth is even recognized in those who would exploit the Tantric teachings as license for any and all acts of pleasure in and of themselves or those who use it merely as a form of sexual magick. He longs for it, seeks after its acquisition. And when he obtains but the smallest morsel of it, he at once realizes the transity of worldly desires.