I'm not sure why the unnecessarily aggressive response
If you have no suggested system that works better, then I see no reason why the existing system is 'not enough'.
Moreover: Strategic games rely on a sense of predictability. Not too much, but hear me out. If you have no idea what on earth your religion is going to develop into, then it's all completely luck based. If it develops based on complicated criteria, then you have no easy way to influence it.
You call it a competitive game but suggest that you do not control the religions that come from your own Civ?
That seems like contradiction in your own argument.
They develop by themselves? What does that mean?
How do you know what's coming?
Just because I suggest we don't remove Player Agency for no reason does not mean I recommend some full creative mode sandbox. I'm literally saying I like this aspect of the game how it is.
So why don't you take the burden of proof about the suggestion instead of strawmanning?
Yeah, probably too aggressive.
Got your attention, though.
The problem as I see it is that the earliest Religious component Beliefs in the game (Civ VI) don't come early enough. Religion may be one of the oldest components of human culture. Some of the earliest examples of ceramics are fired Votive Objects, not Pots. Every early settlement that has been excavated, if enough survived, there is evidence of Religious Places: shrines, altars, sacrificial 'basins', etc. In fact, one of the signs of a non-heirarchial settlement is that there is no central Religious Place: no great temple, or temple square, or ziggurat in the city/town. If every residence in the place has its own little shrine/altar (as at Catal Huyok and other Anatolian neolithic sites) that's a pretty sure sign that 'Priest King" would be a meaningless noise to them.
All of which is a long way of saying I want your initial religious bonus (or malus) to be part of your Starting Position. To simplify a bit, start on the coast, your people should have Fishy Gods - or at least, Wet Ones.
Of course, you could/should also have the choice of a Centralized Religion/Belief of some kind (or several kinds) which will lead you to building the Holy Sites we all know and love, or a Private Religion that will take longer to build any centralized Shrine but gives all your population some extra Bonus.
It's still Gamer's Choice, but an earlier choice and not as complete a choice as we are used to: if I am nowhere near a Desert, why should Desert be any part of my Pantheon?
BUT as the game progresses - Your Religion should Change. Wind up in the late Classical with half your citues in or edging the Desert, and there will be a movement in your population to incorporate the vastness of that desert into the Pantheon. This may start out as just adding a Belief, but also may swap out an older Belief for a new one. That latter is a Hard Sell (look at the dietary restrictions that date back 1000s of years that are still part of 'modern' Religions: that "Ol' Time Religion" is not just a phrase!)
Point is, the Gamer/State/People can nudge, support, even proclaim a 'State' religion and Mandate Beliefs and Tenets, but some wandering prophet (Read: non-State-generated Great Prophet) can wander out of that aforementioned Desert and upend everything - or at least, upend a Lot.
Note that in the Roman Empire, they had a 'state religion' - the Imperial Cult, and it evaporated in the face of both the Mithra Cult (the favorite religion of the Roman Army) and Christianity, and both of those 'wandered out of the desert', so to speak - they weren't Native Roman. BUT Christianity, in turn, adopted the administrative structure of the Roman Empire and kept it going for another 1000 years after the Empire unraveled. In other words, not everything is Replaced completely in religion, and if you are playing the Roman People from 4000 BCE to 2050 CE that 'introduced' Religion could be what keeps you going for an Era or two in the game.
I don't have a complete Structure for Revised Religion in Civ VII (I suspect the design team already has their own in any case). But in the spirit of "1/3 New, 1/3 Revised, 1/3 Same" I think Religion is worth exploring for new ways of portraying it.