This has not been my experience in the past 7 years of addiction recovery. It's been imperative in order to root out as many ways my personality evolved to support addiction and has led to realizing many unconventional ways I've been avoiding my emotions than what's identified by most recovery or 12-step groups. Also, I've made arguments like what you're making before i entered into recovery to explain why i wasn't trying to make comprehensive changes to my life and explain away learned helplessness around changing myself.
My guess is what's viewed as decision fatigue could be unaddressed emotional issues, such as automated judgment/criticism, fear avoidance, normalized disempowerment narratives (which is related to cultivating a growth-oriented mindset, as opposed to one that says "this is just how i am and it can never be different"). Practicing radical acceptance and ignorance, as well as maintaining a playful attitude toward what I'm doing have been monumental to deeply examining myself. All this helps with perfectionism, which i also stopped practicing. Attempting to be thorough and comprehensive in the application of principles to one's life is not an effort in perfectionism; perfectionism is more about how one approaches doing such a thing. I think another term for what I'm referring to here is "monasticism."
These days, I'm also caring for a 4-year old while trying to examine everything we do from a generational trauma perspective. I no longer believe in ego depletion and consider it to be justification for people getting tired of stuffing/processing emotions that arise in the course of things, and potentially needs they're not aware of going habitually unmet. This brings me to another monumental thing i think has helped me in living a principled and intentional life: learning nonviolent communication and developing an awareness of feelings and universal human needs. To my knowledge,there are no studies examining the impact of these practices on decision-making.
I can say this: choosing actions/things based on what I think will meet my needs vs deny them is easy in a society where most decisions aren't oriented toward needs. There are learning challenges along the way, since there can often be no options present that effectively meet needs, so acceptance of the situation and creativity to come up with new options are both really important skills to develop.
As an aside, ego depletion and decision fatigue seem to be concepts without a lot of reproducibility behind them, or with much smaller effect sizes than previously reported.