Answering Jewish / Muslim objections to their faith, Christians frequently appeals to historical research, which illustrates that existence of "semi-god" or godly king etc. was not a strange thing to second Temple Judaism. So, Christianity keeps 2-nd Temple attitude and is not an idolatry., by including more than one person into Godhead. Judaism evolved since 2-nd Temple period towards strict monotheism, where God is not a "complex", but simple unity, and there is no special godly agent for any purpose. Question: why Christianity cannot evolve in the same way and to move towards strict monotheism, i.e. understanding God as a simple and not complex (formed by Trinity) unity.
Part of the issue here is that Christianity — unlike Judaism and Islam — was developed and organized within the Greco-Roman culture. In the ancient Greco-Roman mythology, it was normal and conventional for gods to manifest in physical form and create children with humans. As such, early converts to Catholicism would have expected a story along the line of Heracles/Hercules, and interpreted whatever teachings they received along those lines. Add that early Judaism was not itself strictly monotheistic — it demanded that Jews worship only Yahweh, but implicitly accepted the existence of other Gods that other peoples worshiped — and there was plenty of room for ambiguity. The notion of the Trinity was a way of rationalizing the idea of full monotheism with the folk-expectations of Greco-Roman culture.
Christianity does not violate the principle of 'strict' monotheism, since in the end Christians believe that Jesus and God are the same being. It calls for some conceptual juggling, obviously, but it has never been a contradiction in terms. There's no particular reason for them to rework one of the core tenets of their faith that is something that will remain as long as it is appreciated, and fall away into disuse when and if cultural attitudes shift.