I agree with you about the 30,000 number specifically. Of course, some of those denominational divisions are more about organization than anything else, not necessarily doctrinal disagreement, but nonetheless, there IS a lot of doctrinal disagreement within Christianity. Even when we consider doctrinal divides, the number of Christian groups that disagree with each other on core issues is huge.While I'm not interested in the first half of your polemic (you believe what you believe) I do take issue when people spout outright lies. There are no where near 30,000 denominations, otherwise you're going to have to commit to the notion that Catholicism alone comprises of about 200 of these "denominations" which is clearly absurd. You can't take any remotely distinct Christian group/rite/organisation and call it a "denomination" with anything remotely resembling honesty.
The Nicene and Apostle's Creeds are both rejected by Christians denominations that account for many millions of Christians. The Trinity is rejected by tens of millions of Christians.I grant that mainstream Christianity is hardly a monolithic entity, but it is not even close to the free-for-all that you imply. Looking beyond the obviously fringe sects, we find that there is nonetheless a coherent historical Christian orthodoxy which is more or less agreed upon by all the major historical denominations. The Nicene and Apostles' Creeds are pretty established ground the majority of all Christians worldwide, just for starters.
Another way of looking at it: can you name a single belief that's held by all Christian denominations?