It must have had a starting point, no?
Not necessarily.
Our mental processes are biased towards making such an assumption, but that does not make much of a real difference regarding the actual likelihood that there was a starting point as such for existence and/or for the universe.
Even if we somehow knew that such a proposition makes sense and turns out to be accurate, that would still be no reason to arbitrarily decide that the starting point had a "cause" as such.
Even if we somehow knew that there was a cause, it would not follow that it was somehow intentional, let alone conscious.
Even if we somehow knew (or perhaps at this point a better word would be "assumed") that there was in fact an intentional cause for existence itself, it is quite the jump to conclude from that such a very hypothetical cause would somehow be aware of humanity in any way, shape or form.
Even then, even taking for granted that there is in fact a conscious "first causer", that would in no way, shape or form imply that this causer would be for any reason worth of respect or even attention, let alone worship. Nor would we have any reason to assume that such an entity would have any degree of moral actualization or awareness.
I never quite understood how come the Abrahamics expect everyone else to make so many wild assumptions and think of those as somehow logical when there is literally no reason to and quite a lot of reasons to refrain from doing such a thing.