This question crops up regularly, and I suspect it's the cause of a lot of worry for those just getting to know the teachings. It was for me at one time. The confusion is caused by the ultimate non-duality of knower and known, experience and experiencer.
Once these distinctions are transcended then we cannot talk about experiencing and knowing in the usual way. Both processes are inherently dualistic.
Hence at profound level of Consciousness and Reality all talk is of Identity, Being and Pristine Awareness. The Upanishads tell us there is no intentional consciousness after death. What there would be is something that probably can never make sense to a person who has spent no time exploring the roots of consciousness.
The crucial point is that Buddhism is not epistemological nihilism. This is a kind of nihilism that is also omniscience. By going beyond the knower-known distinction we would acquire a knowledge of knowledge and experience that is of all knowing and all experiencing, not just of some particular knowledge or experience. Hence the Upanishads also say, 'The voidness of one thing is the voidness of all'. That is, when we understand the nature of one thing we understand the nature of all. In the same way, when we understand the nature of knowing and experiencing we do so for all knowledge and all experience.
Bernardo Kastrup has a highly relevant poem on youtube called 'Legacy of a Truth-Seeker'. This is not really an explanation of anything but it covers a lot of the ground. https://www.youtube.com/watch?v=ZgiwVYZM5A8
I feel your opening statement is not quite right. It is the Perennial view that what is fundamental and original is knowing. This is what distinguishes or characterises consciousness. But this would not be a knowing that requires a division into knower and known. It is not what we usually call knowing but Being, the simple fact of 'I Am' that Descartes spotted was not relative and could not be doubted. This 'knowledge by identity' would be the basis for all knowing for the knower would be the identity, the knowledge the knower. There would be nothing to know except the knower.
Theists capture something like this idea when they speak of God spending eternity basking in His own glory or contemplating on His own nature. The connection to Buddhism can be made by way of the idea of 'Godhead', not a God but a state or 'hypostase' of Consciousness and Reality.
This is about 'pure knowing'. Rupert Spira gives a talk on the topic here. https://www.youtube.com/watch?v=GhCcYU_vzIM
He doesn't rush so you may need to make a brew and settle in.
In the end all you can do is test the teachings in your own practice, but it would be important to avoid the idea they are pessimistic.