The rise of the cults of Shiva, Vishnu and Shakti (Durga), weakened the Vedic religion and Vedic gods like Indra, Varuna, Yama, Agni, Vayu, Surya etc. The cults of Shiva and Vishnu became more prominent eclipsing other cults. I do not know when the major cults of Shaivism and Vaishnavism which were even on adversarial terms at times, combined along with minor cults like Shakteyas etc. to form the modern form of Hinduism. The union of Shaivites and Vaishnavites gave rise to the concept of Trimurti of Brahma, Vishnu and Shiva. The rise of the Trimurti concept did not wipe off the Vedic gods, but they became subordinate to the Trimurti, similar to the angels in Christianity.
The Brahma in the Trimurti concept is different from Brahman or Parabrahma in the Hindu philosophy. The Advaita concept propagated by Shankaracharya is monism which considers Parabrahma as the supreme God which has no form, beginning or end. In this concept Brahman is the only real being and the universe is a myth or shadow. "Brahma sathyam, Jagat mithya", so said Shankaracharya. The Advaita concept is considered as the ultimate truth in Hindu philosophy.
Even when acknowledging Shankaracharya as the last word in philosophy The popular Hinduism revolves around the Trimurty concept and worship of them as common practice. The three members of Trimurti are not considered equal in power. Brahma is considered less powerful than the other two, may be because they were the supreme Gods in their respective cults. There are only very few temples where Brahma is worshiped, though he is the Creater. Vishnu is the Preserver and Shiva is the Destroyer. The Shakti of the Shakteya cult was given three forms as Parvati, Lakshmi and Sarasvati and they became the consorts of Shiva, Vishnu and Brahma respectively. The sons of Shiva, Ganesh(Ganapati) and Subrahmanya (Muruka or Shanmukha) are also worshipped. Ayyappa, the deity of Shabarimala Temple, which became controversial due to a recent Supreme Court judgement is also a son of Lord Shiva. Lord Vishnu has no children as such but has several incarnations like Lord Ram, Lord Krishna etc. who are also worshiped as deities. Though the Vedic gods too have temples here and there they are few in number and not as popular as those of Lord Shiva, his consort and sons , Lord Vishnu and his incarnations. The largest Vishnu temple in history was the one built in Angkor Wat in Cambodia by Jayavarman of Khmer dynasty, some thousand years back. The largest Shiva temple was built in Prambanan in Java in Indonesia. It was a complex of 240 temples, the largest one for Lord Shiva. The two smaller ones on either side were of Lord Vishnu and Lord Brahma.