You are ignoring the absolutely insane volume of gear you get from using a Legendary Crest versus running without one.I've played enough of the game to know what's in the shop, and I don't actually see your point that everything is being throttled. I haven't seen any EXP boosts or ways to buy gear; the throttling is, as far as I can tell, just related to gems and the different ways to obtain them. And that is pretty much the crux of my confusion: the pathway from crests to player power is so incredibly inscrutable that it doesn't seem remotely worth the money. Even though I know that power is the ultimate purpose of crests, I can't wrap my head around why someone would see actual dollar value in them even if buying their way to perfect BiS was their goal. I didn't even know that legendary gems had star ratings until seeing the outrage about it, and I still don't know what their star ratings actually mean. I would actually be more inclined to spend money if I could just outright buy legendary gems—that would of course be more brazen and I don't think anyone would be happy about it, but it least it remotely makes sense as to what you'd be spending your money on.
The whole system of buying crests to modify a rift to get gems that are hopefully the right gems to maybe make your character more powerful is so indirect and obfuscated that I can't see why anyone other than outraged streamers would spend money in that particular system and how it was even something Blizzard thought was worth staking the reputation of the game on.