[Sethomas]

What's with the Vatican, full of riches?

19 centuries give you plenty of time to accumulate stuff. For much of history, the Vatican was the only instutition in Europe with any motivation to cultivate art. Maybe this wasn't absolutely necessary, but art as we know it today wouldn't exist without the Church's sponsorship. Also we'd have little knowledge of Classical art, since the Church was the only significant body that sought to preserve ancient works. The fruits of these labors are available to everyone who wishes to see them, regardless of faith.

Oh, and despite the fact that it entertains millions of visitors every year, the Vatican's standing revenue is less than that of many universities.

What's with all the icons?

In short, why not? Despite slander to the contrary, we don't ever idolize them as anything more than just works of man, so claims of "worshipping graven images" are unfounded.

What's with the veneration of the saints? The veneration of Mary?

In a mild sense of the term, this veneration is no different than the interest a patriot has for the founding fathers, or the pride someone has for his heritage. It's not like we are allowed to worship Mary or the saints, we merely pray to them for intercessions. It's the exact same logic as asking a friend to pray for you when facing trouble.

Speaking in Latin

Latin was the most universal language. A uniform language prohibited the decay of meaning by repeated translation. The world has moved on from this. So have we.

wearing elaborate costumes

Dignity and respect of God's presence in the Eucharist.

the chanting of ritual response when the priest says a certain phrase

That's an ad hominem attack of aesthetics. There's no logic in saying that mass should be done differently every time. Every mass is the exact same celebration of God, with the exact same emphasis on the presence of Christ. Logic dictates that we should develop a working protocol, and implement it universally. That's why the very word "Catholic" means "universal", that's why mass in Germany has the exact same elements as mass in the US.

I think Catholicism is the most ludicrous intrepretation of the message of the Bible one could come to without the use of heavy psychedelics.

Nah, I think you have to admit that Latter Day Saints are worse. Besides, we wrote the New Testament, we were here first, so interpretting the message of the Bible into our protocol is our prerogative.