they do seem like monarchies I agree, but most muslims who research in depth about the caliphates will tell you that the first 250ish years after the prophets (pbuh) death was legitimate under islamic guidelines. the leadership went from companions of the prophet and switched off based on that. they were well respected & were chosen based on the fact that they were present to witness the beginning of islam. they had the credibility & experience needed, plus not all were related to the prophet so it wasn’t like one family ruling. somewhere along the way though, the caliphate leadership turned into family fueds and typical politics you’d expect from expanding empires. they still practiced islam & spread it but by the centuries it was weakening in terms of the meaning of a caliphate.

the idea that power passes from father to son and so on isn’t necessarily unislamic, but the hoarding of wealth and calling humans “king” or “queen” isn’t allowed. those are the main aspects that makes saudi monarchy unislamic in nature, then you add their hypocrisy, extreme laws, & terrible foreign policy that opposes many poorer muslim nations.. no doubt they cannot claim the religion when it suits them. caring for the holy cities makkah & madinah is the only thing they do well