Fairly recent EA here (interested for ~2 years, took the Try Giving pledge a year ago, went to one EAGx earlier this year)
FWIW, I took the GWWC assessment to be both low confidence and out of date, but chose to support Cool Earth anyway despite considering it lower impact than eg health or poverty reduction because I wanted to contribute specifically in aid of climate change mitigation.
My decision process was basically to decide that I wanted climate change to be a focus area for some giving, then go and try and find the least worst charity from an EA perspective. But I still only ever thought of Cool Earth as a least worst sort of option.
I was already planning to cancel my regular donation before I read this (I bought a house and have paused all monthly donations, I will instead donate in a lump sum at EOFY), and will stick with that plan having read this.