Another reason for the abolition of the worship of Brahma/Prajapti according to Shruti. This happened around 2,000 BC.
"Let us next see what traditions about the intermediate stages have been preserved. First of all I refer to the tradition of Rudra killing Prajapati, the god of time, for receding towards his daughter Rohini. The Aitareya Brahmana (iii. 33) describes this conduct of Prajapati as ‘akrita’ (in the sense of 'not done') or unprecedented and such as deserved to be severely noticed by the gods. Can we not herein discover the fact that the sun was gradually receding towards Rohini, by the precession of the equinoxes? The ancient priests, who observed the fact as they watched the Nakshatras at the commencement of the year, could not account for the change, and they rightly and honestly believed that it was a great calamity that the sun or Prajapati should thus follow an unprecedented course.
I Have previously referred to a verse from Garga, which says that if the Uttarayana commenced otherwise than from the asterism of Dhanishtha, it foretold a great danger; and we may suppose that the Vedic Aryas similarly believed that if the sun ceased to commence the year from Orion, it was an unprecedented calamity. Prajapati, however, was punished for his unusual conduct, and there the matter ended for the time being. I may also refer here to the ancient mode, of deriving the word Rohini. The Arabs called it Al-dabaran (English – Aldebaran) or “the follower” evidently because it came next after the- Krittikas. But the Hindus called it Rohini, "the ascended", inasmuch as they noticed that the sun gradually ran towards it in oldest days. It has been suggested that we should explain the legend of Prajapati by (reference to the daily rising of Rohini, Mrigashiras, and Rudra in succession.
But this explanation hardly accounts for the fact why Prajapati was considered as literally running after Rohini in an unprecedented way. Surely we cannot suppose that the Vedic priests were ignorant of the fixed position of these constellations, and if so, we cannot account for the fact why they considered Prajapati as running after and thinking of living together with Rohini unless they had noticed the actual recession of the sun towards Rohini owing to the precession of the equinoxes. The tradition of Prajapati and Rudra, is thus comparatively speaking a later tradition though it seems to have been completely formed before the separation, of the Greeks and the Iranians from the Indian Aryans."
"Orion or the researches in the Antiquity of Vedas", Bal Gangadhar Tilak, Page 213-14.
It is much easier to worship God with form, such as Krishna, Vishnu, Durga, Shiva etc.
