What is this missing ingredient between Jhanas and Nibbana?

[pyluyten]

i consider your question to be a very good one

a) sutta do not call "arupa" attainments "jhanas" ( there is no "arupajhana" in suttas)
b) jhana, are not a distinct practice from vipassana. Jhana are both samatha and vipassana.
c) some sutta say buddha was taught arupa attainments

so we have many possible conclusions here

i) jhana were already taught, and so nibbana
ii ) jhana were already taught, but not nibbana. The missing ingredient is either in the way of life side, or in the knowledge side.
iii) "arupa" were taught, but not jhana. Buddha taught jhana and nibbana, and there is no missing ingredient appart of course jhana are part of the Path.

[auto]

Beings do the things they do because of passion, ignorance or aversion.
At the same time if you do something long enough time you get dispassion, learn or get used to it.

So logic is if you have dispassion arising, you don't want to watch TV anymore then you should force yourself to continue watch TV and see what you otherwise out of habit always not see. So there is lot of things you don't experience because of various conditions affecting you to quit.

So jhana factors are the helpers what help you stay with the object. So eventually if you get through 3rd jhana what is either too good or too bad you get to equanimity. Anyways you should notice also mind(namarupa) what is free from the object.
..

[form]

There are only 4 jhanas.