Well, this is true but as you seem to be well read on history you do understand how premodern societies worked, do you? Even a 10 percent tax was a huge burden due to very little wealth flowing around. So everything you mention here is true, but applies to certain Islamic societies at certain times. The issue is, at that time Orthodox Christianity was still a good enough of an alternative for these societies. So of course opposed Islam. Not so in the current age, which you can see if you travel to an Orthodox country like Serbia, which is full of reality TV sluts and other nonsense.