Back then, the Quraysh Tribe had adopted the teachings of Prophet Abraham a.s and Prophet Ismail a.s which is Tawhid. They know Allah. However, they went astray.
"And if indeed thou ask them who it is that sends down rain from the
sky, and gives life therewith to the earth after its death, they will
certainly reply, "(Allah)!" Say, "Praise be to Allah." But most of
them understand not." (Translation by Yusuf Ali)
Al-'Ankabut verse 63
"Say: "Who is it that sustains you (in life) from the sky and from the
earth? or who is it that has power over hearing and sight? And who is
it that brings out the living from the dead and the dead from the
living? and who is it that rules and regulates all affairs?" They will
soon say, "(Allah)". Say, "will ye not then show piety (to Him)?"
(Translation by Yusuf Ali)
Yusuf verse 31
"Abraham was an exemplary leader, devoted to God, a monotheist, and
was not of the polytheists. Thankful for His blessings. He chose him,
and guided him to a straight path. And We gave him goodness in this
world, and in the Hereafter he will be among the righteous. Then We
revealed to you ˹O Prophet, saying˺: “Follow the faith of Abraham, the
upright, who was not one of the polytheists.” (Translation by Talal
Itani and Dr Mustafa Khattab)
An-Nahl verse 120-123
Back then, the Quraysh Tribe also fast
"Quraish used to fast on the day of 'Ashura' in the Pre-Islamic
period, and Allah's Messenger (ﷺ) too, used to fast on that day. When
he came to Medina, he fasted on that day and ordered others to fast,
too. Later when the fasting of the month of Ramadan was prescribed, he
gave up fasting on the day of 'Ashura' and it became optional for one
to fast on it or not."
Back then, In the period of Ignorance (Jahiliyyah), i'tikaf was already known.
"`Umar asked the Prophet (ﷺ) "I vowed in the Pre-Islamic period of
ignorance to stay in I'tikaf for one night in Al-Masjid al-Haram." The
Prophet (ﷺ) said to him, "Fulfill your vow.""
And Allah knows best.