Hari Om. The entire teaching has been handed down by a guru shishya parampara tradition. Lord Krishna has Sri Sandeepany as His guru. Regarding others, of course they have had some guru to impart them the knowledge , though we know Buddha strived to attain enlightenment Himself.
As there are so many hospitals and doctors around the world and yet illness is rampant, new diseases manifest and we have no cure yet for many serious diseases – we cannot write off the health professionals. In the same way, there are spiritual gurus around the world – and yet there is so much negativity in society.
Two things – first it is true that today not all spiritual gurus are completely sincere and there is a culture of what a Buddhist teacher called ‘spiritual materialism’. Second, at least countless people are benefitting from diverse spiritual teachers and teachings – can we imagine how bad it would be if we did not have any spiritual gurus? Even today we see many people have evolved, there is a consciousness regarding spirituality and an effort to seek peace and happiness through spiritual pursuit.
I do agree with you that there are many imbalances in society and that is why we have to work harder to bring more awareness so that the collective consciousness can change. Even if a few of us transform it can permeate the society! I am optimistic!