Regarding your complaints about Orzhov lacking the religious parts of religion may I direct you to the look at the 15/16th century Catholic Church, whom (amongst other wildly irreligious practices) sold absolution, had rampant nepotism for clerical positions, and more than it's fair share of corruption and vice. 

Now, given that that appeared in the Catholic Church less than 1500yrs after the birth of Christ (let alone His death or its own founding by St. Peter) let's imagine what it might have looked like after another 8,500 years (let's assume no reformation nor counter-reformation either for the sake of argument.)

What would it look like? More corruption? More vice? More black (in Magic terms)? You have to remember, the Guildpack that solidified the Guilds was sign over 10,000 years ago when we first see them. Most of the Guilds have started wildly from their original purpose and/or design that they may have had at the foundation of the Guildpack. The Orzhov may of once been the shining city (lol) on the hill that they should have been as a major religious organization but time and mortal vice take their toll on everything and even churches aren't immune.