Brahman according to the Upanishads is ekamevadvitiam, i.e., one without a second. There is no second person to worship Brahman. Moreover it is stated quite clearly:
That which cannot be comprehended by the mind but by which the mind is
cognized know that alone to be Brahman, and not this that people
worship here.
Kena Upanishad I.6
Brahman is nondual in nature and hence is not worshiped. The Deities and the Supreme Being, Isvara, is at the level of duality and can be worshiped.
All the deities are channels to the Supreme.
Sri Suka said, "One who desires to have the lustre of Vedic learning
should adore Brahma from whom the Vedas have come; those who seek
power of the senses should worship Indra, and those who desire
progeny, the Prajapatis. The seeker of wealth should worship Sri Devi;
of brilliance, the deity Agni; of wealth, the Vasus; and of power, the
Rudras. The seekers of food stuffs should worship Aditi; of heaven,
the twelve Adityas; of kingdom, the Visve-devas; and of popularity,
the Sadhyas. The seeker of longevity should worship the Asvinidevas;
of strength of body, the Bhumi Devi; and of security, Dyo and Bhumi
who are the parents of the worlds. The seekers of beauty should
worship the Gandharvas; of women, the Apsara Urvasi; and of
sovereignty over all, Brahma, the Lord of the worlds. The seeker of
fame should worship Vishnu; of immense wealth, Varuna; of learning,
Parameswara; and of happy conjugal life, Uma. The seeker of Dharma
should worship Vishnu as Uttamasloka; and of increase in progeny, the
Pitris; of security from possession by ghosts, Yakshas; and of
strength, the Maruts. The seeker of kingdom should worship the Manus
and the Devas; of the destruction of enemies by black magic, the
Rakshasa Nirritti; and of sexual satisfaction, Soma. But those who
have no desires worship the Supreme Being who transcends Nature. But
the one Being to be adored with intense devotion by all - whether they
be devoid of all desires, or whether they be desirous of all
enjoyments, or whether they be seekers of Moksha - is that Supreme
Person, the one God of all. (In other words all the Deities mentioned
above are nothing but His manifestation, and all their powers stem
from Him alone. So a man of intelligence worships the Supreme Being
alone through all Deities.) The ultimate object of all worship is the
generation of unswerving devotion to the Supreme Being. It leads to
liberation, the highest destiny of man. By association with holy men
devotion develops in an aspirant.”
Srimad Bhagavata Purana II.3.2-11