The Katha Upanishad (1:2:23) teaches that truth cannot be known through scripture, only mystic experiences alone. The Hindu swami Sivandada, quite in contrast to the Bible's admonition to use one's "power of reason" says "Intellect is a hindrance. That which separates you from God is mind."-The World of Gurus, page 77.
The focus of Swami Sivananda here is experiential understanding rather than mere intellectual understanding of Brahman or God, which does not get anyone anywhere. I have emphasized this in this
post.
Prajñanam brahma - Brahman is pure consciousness (Aitareya Upanishad 3.3 of the Rig Veda)
Brahman being pure consciousness, is subtler than thought or intellect, and this is the reason why consciousness is considered the right instrument to perceive Brahman. Here consciousness is consciousness purified of impurities of intense desires in the form of cravings and aversions, through meditation, selfless service, present moment awareness and unconditional love.
Hindu mystics practice Yogic meditation so they can dull their intellect and experience trances, feelings of ecstasy. Those who attain such a state ares said to have achieved moksha.
It is not dulling of the intellect, but purification of consciousness through meditation that is emphasized here.
In fact research has confirmed meditation to be associated with superior cognitive benefits.
Yoga, meditation improve brain function and energy levels, study shows
Meditation's cognitive benefits | About memory
The Yoga Sutra does not refer to fallen angels or wicked spirits as such it calls them celestial beings, in this case it warns against the possible contact with evil celestial beings.
It is just the projections of imagination being dealt here. There are no such things as Satan and demons in Hinduism which you are accustomed with. That is why you and others are imagining things where there is none.
In fact, reasoning and discretion is also emphasized in the Yoga Sutras.
1.17.The concentration called right knowledge is that which is followed by reasoning, discrimination, bliss,unqualified ego.
Those who have vices in them are called demonic, but it is really the vices within them stemming from raag-dvesh, intense desires in the form of cravings and aversions that are the true causes of demonic nature.
All crimes such as murder, rape, torture, theft can be traced to cravings and aversions known in general as hatred, lust, anger, greed and so on. This is all there is to it. The real adversary is not Satan, demons, ghosts or Dracula but
the untrained mind.
Whatever harm an enemy may do to an enemy, or a hater to a hater, an ill-directed mind inflicts on oneself a greater harm. Neither mother, father, nor any other relative can do one greater good than one’s own well-directed mind. - Buddha ( Dhammapada 42-43)
For him who has conquered the mind, the mind is the best of friends; but for one who has failed to do so, his mind will remain the greatest enemy. Krishna ( BG: 6.6)
It is the untrained mind that is known as Maya in Hinduism and Mara in Buddhism. It is the untrained and conditioned mind that projects such deluded fantasies as Satan and demons and evil celestial beings which some take as literal and real, and run circles around it all their lives.
This deluded state can also be caused by ill-health, psychological disease and senility.