Sri Krishna said in B.G.:
मां च योऽव्यभिचारेण भक्ितयोगेन सेवते।
स गुणान्समतीत्यैतान् ब्रह्मभूयाय कल्पते।।14.26।।
Whosoever serves Me alone with an unfailing devotion-Yoga, he, transcending these Strands, turns to be the Brahman.
One must understand that the purpose of reaching highest stage in SPIRITUALITY/BRAHMAN, is to attain ABSOLUTE BLISS , but not to attain powers/siddhis .
Attaining powers/siddhis or concentration, etc, may occur as a consequence of doing mantra japa or meditation , etc.
In the case of some persons, this may result only in ABSOLUTE BLISS but not in attaining powers.
Sri Krishna in earlier era, Sri Shirdi Sai in our era exhibited Superhuman powers, whereas Sri Ramana Maharshi did not.
It depends on one's prArabdha (stored merit of the body).