I find the prestige levels after 15 make the game less fun so I've been enjoying staying at 15, here are my favorite things to auto-pick in descending order, in terms of power:

Baptism of Fire

"Every 3 burnt Blightrot Cysts lowers Hostility by 10. While the Hearth is corrupted, you're unable to sacrifice resources."

S tier. This cornerstone is basically an auto-win. Funnily enough, if you play on at least Prestige 3 where you get a bunch of blightrot cysts every 3rd year for free this becomes even more powerful. I typically end the game with 0-2 hostility level when I can snag this since rain engines are really really really strong.

Foxes

S tier. I can't say enough good things about foxes although they aren't necessarily OP, they just make the game survivable until you can get to the OP stuff. Their most powerful trait is speeding up glade events which makes timing everything so much more forgiving and you can get away with opening a dangerous glade before Year 1 Clearance season. This alone makes them worth it but they are easy to keep above 0 resolve, have a low blue resolve threshold, get bonus resolve from porridge (which is the easiest complex food to make) and they have a bonus when working inside the beanery or distillery which makes porridge. Rainwater is really powerful and being able to pop one or two into a geyser to save Living Essence for another Hearth while not running out of water can be game changing. They're also the second best flame keeper and, if you've been opening a lot of glades, the best in the late game.

Temple

"For every 200 seconds spent sacrificing goods in the Ancient Hearth, Hostility is reduced by ‑25 "

A tier. This building can instantly turn around a bad run. This is also an instant win if you have a grain oil supply chain and can pop a rain engine into your oil producing building. If you 3x sacrifice oil the added production speed can allow you to make more oil than you're sacrificing, allowing you to reduce hostility by 200 in a single year and repeat it infinitely.

Small Farm

A tier. I try to maintain a cadence of 1 dangerous glade per year but if I can find fertile soil I breathe a sigh of relief since grain from Small Farms is the foundation of a lot of powerful production chains:

• Grain -> Meat (via ranch) -> Skewers Jerky
• Grain -> Porridge
• Grain -> Oil
• Grain -> Oil / Flour -> Pack of Trade Goods
• Grain -> Flour -> Biscuits Pie

There are situations where you'll want vegetables but the above are really strong. If I can establish one of these I can slow down on dangerous glade opening and build a reserve of resources.

Rain Engines

B tier. All sources of double production in general are pretty powerful but rain engines with everything dialed up are always worth the investment of having to deal with blightrot, hunting for water sources, building the geyser, staffing the geyser with labor or the robot. The resolve bonus can make a building with a rain engine a safe haven for a species that's at risk of leaving, even if it's not producing anything, which is nice. Using rain has a powerful synergy with cornerstones and orders, especially the cornerstone that reduces hostility per rain used in rain engines, although that one's slower to ramp up than Baptism of Fire.

Lumber Yard

C tier (still OP). I fell out of love with the Lumber Yard between unlocking the Workshop and Prestige 10 but the Lumber Yard is really versatile. You're guaranteed to need a lot of planks so being able to efficiently turn wood into planks takes some stress off your wood production needs so you can more safely pluck out wood cutters to stay within your desired hostility threshold or save up absurd amounts of wood later on to sacrifice for resolve reputation or to power up your temple. I also like having Beavers on my team and they have a nice bonus in the Lumber Yard. But the hidden star of the show is the access to producing Pack of Trade Goods. If you can set up a Grain -> Oil / Flour pipeline then suddenly the trader is usable again even with the price bump and value decrease from Prestige.

Conclusion:

I'll likely change my opinions and add stuff to this list as I find more things that are OP or change my playstyle. My playstyle currently is to minimize hostility, open 1 dangerous glade a year, avoid small glades, deprioritize tools and containers, build hearths as soon as I have space, and not rely on traders or scaling that depends on amber.