Interesting. Is it because they spend too much time researching it? How early is too early for a religion?
It's because they many times ignore some of the basic technologies and take too long to boost commerce and get a proper defense. Many times they will even go straight towards the technology that is unlocked by the religion ignoring everything else.
I guess that this is also why on low difficult levels you sometimes encounter an AI spending too much time with just warriors.
On my Clan of Embers game diary, Decius researched Runes even without Calendar (and I don't remember him having any wine or gold so that crafting and mining was worth it in terms of commerce boost).
Without the Diety bonuses, what would he do to grow, increase his happy cap and get some basic commerce from resources early on? Even on diety he was not able to get away with that bad decision-making.
The three early religions must be bulbed always. There isn't a reason to not bulb them. That's how you can get them fast without falling behind in commerce and defense.
One always need mysticism to get a religion, so research that, switch to God King and pacifism (with God King you can build warriors fast enough without nationhood), start building a temple and afterwards run a priest. Meanwhile, you research with your land commerce the other necessary technologies to be able to get the religion.
If you want Runes you need mining, so you go towards that in the normal way and the priest will do his thing - you are basically doing two researches at the same time.
Depending of the traits of your leader and your land, you may be able to get runes at more or less the same time that you finish researching mining.
This is much faster, way more effective and also safer.
If the AI becomes able to do this (no idea how) it will be much harder up to rush it and it will tech more effectively early on.
Also interesting. I almost never use GP for researching techs (but then again, I play on Monarch level myself). When and why do you use this option rather than settling them or getting a golden age or building?
Bulbing strategies are a little bit more complicated than just simply farming everything and running aristocracy but they are fine with a philosophical leader.
You have to plan ahead and know the bulbing order.
A philosophical leader using guilds with big cities will be able to research multiple paths at the same time using bulbs. Since you're just basically using mostly fat farms and specialists, golden ages will not boost your commerce (but they do give a boost to GP growth).
A financial leader will just continue to use land commerce and Golden ages to boost that.
I can't give you a specific answer because it depends on your goal. Just plan ahead so that your research progression is faster with the help of bulbs.
On my White hand game, even though auric is not philosophical, I'll demonstrate a little bit of bulbing for late game technologies.
Reading your diaries is useful. Though it's a little easier when I get specific comments such as the ones quoted above, or 'the AI doesn't value iron enough', or "more Pyre Zombies", etc. Then I have a specific spot in the code that I can go to and start working from.
I am wondering, though, if you don't have too many written notes and things to do already.
Sometimes it's complicated to be specific since the AI screws up not because of just one mistake but because of a serie of small things.
You know that they don't tech effectively, you know that they don't handle their troops well enough still, and you know that they don't evaluate power properly (they're way better than vanilla, of course

).
The AI is also incapable of "foreseeing" summons which makes it incapable of reacting properly to them.
Iron working should definitely have more value to the AI.
I also once commented that the current emphasis on drill promotions is probably not good. Warriors with just drill promotions are just asking to be rushed. Warriors are too weak and need combat promotions. Drill promotions are mostly for units that are already strong enough.
I also wish that the AI would consider more stuff when settling (like culture pressure, the overall quality of the tiles (they will settle on the ice if there is just one resource there)) instead of mainly the resources.
Make Auric AI stop spamming javelin throwers early on To attack cities and research Iron working and I'm sure that he will be one of the strongest AIs in the game.
Well, I better stop now. I am just repeating some of the things already said. There is no point in adding more stuff if there is still a lot of planned stuff to do.
- Major overhaul of the AI teching routines. The AI now takes a lot more factors into account and should be better at reacting and adapting to its current situation. This will be an ongoing area of work.
- AI will actively seek out and explore Lairs and Dungeons (land and sea)
- AI will be better about picking up its own equipment
- Cast and resist messages will display the spell name and the name of the casting unit (also fixed a bug that was causing extra resist messages to appear)
Awesome

But hopefully the AI will explore lairs with strong enough units

.