What the Rav said:
Moshe Rabbenu, by himself, can’t say Kaddish.
If he were to say Kaddish, it would be a Kaddish in vain. A bracha in vain.
If we saw him now go out to the field to do hitbodedut and we said to him, Moshe Rabbenu, say Kaddish. He can’t.
He needs ten shoe-makers, ten tailors, ten sewage cleaners, to say Kaddish with him. The main thing is that they keep Shabbat.
There are things which can only be rectified by a gathering of souls.
You can’t make your tikkun (rectification) alone.
We can’t achieve our tikkun alone.
We need to get married.
We need to have a chavruta.
We need to engage in ‘maseh u matan’ (business).
It would be much easier if we could sit on a hill somewhere, by ourselves, not being bothered by anyone, and achieve our tikkun that way.
But, we can’t.
We have to engage with others. We have to bitul (nullify) ourselves to others. We have to accept the difficulties and the bizayon that comes along with all those relationships…
That’s how we’ll reach our tikkun.